Part 4

----+--------+-------+-------------+--------------+-------+----------- 247| 1,295 | 200 |2.5 hours |Survived |Oats |Gray. 248| 1,305 | 200 |3 hours | do. | do. | Do. 337| 1,040 | 211 |1.5 hours | do. |Carrots| Do. 336| 1,045 | 211 | do. | do. | do. | Do. ----+--------+-------+-------------+--------------+-------+-----------

SERIES C.

----+--------+-------+-------------+--------------+-------+------------ 122| 2,060 | 250 |2 hours |1.5 days |Oats |White. | | | 55 minutes | | | 234| 1,650 | 242 | |About 24 hours|Carrots| Do. 335| 1,170 | 240 |1 hour | do. | do. |Gray | | | | | |coccidiosis. 249| 1,185 | 236 |4 hours |Survived |Oats |Gray. 321| 1,135 | 246 |2 hours | do. | do. |Yellow. | | | 10 minutes | | | 250| 1,435 | 252 |4 hours | do. | do. |Gray. | | | 35 minutes | | | 334| 1,270 | 240 |1 hour | do. |Carrots| Do. 233| 1,675 | 238 |6 hours |26 hours | do. |White. | | | 10 minutes | | | ----+--------+-------+-------------+--------------+-------+------------

SERIES D.

----+--------+-------+-------------+--------------+-------+----------- 253| 1,600 | 275 |10 minutes |35 minutes |Oats |Brown and | | | | | | black. 252| 1,335 | 270 |30 minutes |4 hours | do. |Black. | | | | 55 minutes | | 327| 820 | 292 | |2 hours | do. |White. | | | | 15 minutes | | 340| 1,465 | 273 | |About 18 hours| do. |White and | | | | | | brown. 341| 1,450 | 270 | |1 hour | do. | Do. | | | | 25 minutes | | 326| 1,645 | 243 |2 hours |50 hours | do. |White. 235| 1,875 | 267 | |20 hours |Carrots|Gray. 316| 860 | 267 |2 hours |3 hours |Oats | Do. | | | 45 minutes | 20 minutes | | 395| 1,410 | 283 |3 hours |Survived | | Do. 395| 1,215 | 275 | do. |About 2 days |Oats | Do. 396| 1,475 | 272 | do. |Survived | do. | Do. 396| 1,245 | 275 |1 hour |About 18 hours| do. | Do. 397| 1,375 | 290 | |3 days | do. | Do. 398| 1,570 | 293 | |5.5 hours | do. | Do. 399| 1,725 | 300 | |6 hours | do. | Do. ----+--------+-------+-------------+--------------+-------+-----------

SERIES E.

----+--------+-------+-------------+--------------+-------+------------ 325| 1,065 | 112 |2 hours |Less than | Oats |White female. | | | | 22 hours | | 330| 935 | 107 |None |Survived | |Gray. 329| 775 | 103 |do. | do. | |Gray male. 320| 1,040 | 115 |2 hours |46 hours | Oats |Black male. 551| 1,450 | 100 |30 minutes |Less than | do. |Gray female. | | | | 24 hours | | ----+--------+-------+-------------+--------------+-------+------------

ADMINISTRATION BY MOUTH.

These experiments were carried out on two varieties of rabbits, the white and the gray. The diet consisted chiefly of oats, but in a few cases carrots formed the exclusive diet. Food and water were given ad libitum. A 2 per cent solution of caffein was administered through a stomach tube. Since the resistance to most drugs is commonly supposed to be greater when given by mouth than when administered by any other path, doses of 175 to 200 mg per kilo were fed in a series of preliminary experiments, all of which were performed on gray rabbits weighing from 865 to 1,135 grams, and which were fed carrots for several days previous to the experiment. Three of the rabbits survived, two without showing any symptoms; in the other case paralysis of the posterior extremities was observed five hours after he received caffein and he was found dead the next morning. Unfortunately no autopsy was performed. The low resistance to caffein of this animal was probably due to some abnormal condition which developed about the time of the experiment, since this rabbit received 325 mg of caffein per kilo two weeks previously and increased reflexes only were observed as a result of this treatment. Hence 200 mg of caffein per kilo can not be considered the toxic dose when fed by mouth. In the following experiments larger doses were therefore given.

SERIES A.

_Rabbit 248. Belgian hare. Weight, 1,170 grams. Diet, oats._

November 17: 1.20 p. m., 19.5 cc 2 per cent caffein (330 mg per kilo) administered by the mouth; 4.30 p. m., somewhat hypersensitive.

November 19: No symptoms; at 9 a. m., urine collected, no reduction of Fehling's solution; rabbit survived.

_Rabbit 241. White male. Weight, 1,380 grams. Diet, oats._

November 17: 1.15 p. m., 20 cc 2 per cent caffein (290 mg per kilo) administered by the mouth; 4.30 p. m., some hypersensitiveness, but no other symptoms.

November 18: 9 a. m., urine collected, no reduction of Fehling's solution; no symptoms; rabbit survived.

_Rabbit 249. Belgian hare. Weight, 890 grams. Diet, oats._

November 17: 1.30 p. m., 14.5 cc 2 per cent caffein (325 mg per kilo) administered; 4.30 p. m., hypersensitiveness; no other symptoms.

November 18: 10 a. m., no symptoms; urine collected, no reduction; rabbit survived.

SERIES B.

The object of these experiments was to determine the minimum fatal dose of caffein in the two varieties of rabbits, the white and the gray. All of the animals selected were approximately of the same weight.

_Rabbit 239. Belgian hare, male. Weight, 935 grams. Diet, oats._

November 19: 4 p. m., 17 cc 2 per cent caffein (363 mg per kilo) administered by mouth, followed by 10 cc of 0.9 per cent salt solution.

November 20: Urine examined, no sugar found, no symptom noticed at any time after injection.

_Rabbit 254. Belgian hare, female. Weight, 975 grams. Diet, oats._

November 19: 4.05 p. m., 18 cc 2 per cent caffein (369 mg per kilo) administered by mouth, followed by 10 cc of 0.9 per cent salt solution.

November 20: 9 a. m., rabbit found dead.

_Rabbit 267. White. Weight, 1,050 grams. Diet, oats._

November 23: 12.10 p. m., 18 cc 2 per cent caffein (342 mg per kilo) given by mouth, followed by 18 cc salt solution; 1 p. m., increased reflexes, tremors marked but no tetanus; 1.05 p. m., rabbit stretched on abdomen, posterior extremities in extended position and paralyzed, soon after clonic spasms set in, which recurred about every minute; 1.14 p. m., tetanus and death. _Autopsy_: Liver showed fatty degeneration; slight inflammation of stomach and intestines; other organs normal.

_Rabbit 268. White. Weight 1,100 grams. Diet, oats._

November 23: 20 cc 2 per cent caffein (363 mg per kilo) administered by mouth, followed by 20 cc salt solution; 1.15 p. m., somewhat hypersensitive; 4.30 p. m., tremors fairly marked, no urine passed, about 2 cc of bloody looking urine obtained from bladder, which contained albumen and a considerable amount of glycogen; rabbit died.

_Rabbit 419, Belgian hare, male. Weight, 1,600 grams. Diet, oats._

September 26: 10 a. m., 28 cc 2 per cent caffein (350 mg per kilo) given by mouth; reflexes increased at 4 p. m.; 6 p. m., reflexes still increased, no other symptoms.

September 27: 9 a. m., found dead. _Autopsy_: Lungs, liver, and kidneys congested; other organs normal.

_Rabbit 420. Belgian hare, male. Weight, 1,250 grams. Diet, oats._

September 26: 10 a. m., 22 cc 2 per cent caffein (352 mg per kilo) given by mouth; 11.35 a. m., convulsions; 12 noon, found dead. _Autopsy_: Liver showed very extensive coccidiosis; no other lesions.

_Rabbit 421. Belgian hare, male. Weight, 1,485 grams. Diet, oats._

September 26: 10 a. m., 26 cc 2 per cent caffein (351 mg per kilo) administered by mouth; 4 p. m., reflexes increased; 6 p. m., reflexes as before, no tetanus observed.

September 27: 9 a. m., rabbit found dead. _Autopsy_: Congestion of lungs and kidneys; liver congested and slightly fatty.

_Rabbit 424. White, male. Weight, 1,295 grams. Diet, oats._

September 26: 2 p. m., 19 cc 2 per cent caffein (293 mg per kilo) administered by mouth; 4 p. m., reflexes increased, no other symptoms; 6 p. m., no change since 4 p. m.

September 27: 12 noon, convulsions and death. _Autopsy_: Congestion of the lungs; no other lesions.

_Rabbit 423. White, male. Weight, 1,205 grams. Diet, oats._

September 26: 2 p. m., 18 cc 2 per cent caffein administered by mouth; 4 p. m., reflexes increased, no tetanus; 6 p. m., condition unchanged since 4 p. m.

September 27: 9 a. m., found dead. _Autopsy_: Lungs, liver, and kidneys congested; other organs normal.

_Rabbit 422. White, male. Weight, 1,440 grams. Diet, oats._

September 26: 2 p. m., 21 cc 2 per cent caffein (291 mg per kilo) given by mouth; reflexes increased at 4 p. m.

September 27: 3 p. m., alive, no symptoms; 4 p. m., convulsions with recovery, this was soon followed by a violent attack of tetanus, which lasted about one minute and was succeeded by paralysis; rabbit died at 4.30. _Autopsy_: Liver slightly congested; a small portion of the intestine showed congestion and edema; other organs normal.

A study of these experiments shows also considerable variation in the toxicity of caffein when given by mouth. In some cases a dose of 300 mg per kilo, and even less, caused death, as in rabbits 423 and 424. In other rabbits, however, approximately the same doses of caffein produced increased reflexes only. The same symptoms were produced in Nos. 248 and 249 after the administration of 325-330 mg of caffein per kilo, while another rabbit (No. 239) survived a dose of 363 mg per kilo. That this is exceptional, however, appears from the result of the following experiments on rabbits Nos. 419, 420, and 421, all of which died after receiving 350 mg of caffein per kilo, and rabbits 267 and 268, to which doses of 363 and 342 mg, respectively, per kilo proved fatal. It will be observed further that the gray rabbits are more resistant to caffein than the white animals, as 350 mg per kilo was the smallest fatal dose for rabbits 419, 420, and 421, all of which were gray rabbits, while a dose of 290 mg per kilo was fatal for some of the white rabbits. Again, it will be noticed that of the two gray rabbits, Nos. 254 and 239, which received the largest doses in these experiments, namely, 369 and 363 mg, respectively, one survived. The largest doses given to the white rabbits were 363 and 342 mg caffein per kilo. Both of these died from the effects of the drug. It may be concluded, therefore, that the minimum toxic dose for the gray rabbit is about 325 mg of caffein per kilo, and the minimum fatal dose is at least 350 mg per kilo. It is to be remarked in this connection that post-mortem examination showed extensive coccidiosis in rabbit 420 and fatty liver in No. 421, while the macroscopical examination of the organs of Nos. 424 and 423 failed to show the presence of such abnormalities. Since, as was observed in the section on subcutaneous injection and elsewhere in this investigation, pathological changes are apt to decrease the resistance to caffein, it is quite possible that 350 mg per kilo is not the minimum fatal dose for the normal rabbit. Indeed, the experiment on rabbit 239 lends support to this view, thus furnishing additional evidence of difference in the resistance to caffein in the two varieties of rabbits.

TABLE 2.--_Administration of caffein by mouth._

SERIES A.

+--------+-------+-----------+--------------+-------+----------- Rabbit| |Caffein| | Duration | | No. | Weight.| per | Symptoms | of life. | Diet. |Remarks. | | kilo. | | | | ------+--------+-------+-----------+--------------+-------+----------- |_Grams._| _Mg._ | | | | 248 | 1,170 | 330 |3 hours |Survived |Oats |Gray. | | | 10 minutes| | | 241 | 1,380 | 290 |2 hours | do. | do. |White male. | | | 15 minutes| | | 249 | 890 | 325 |3 hours | do. | do. |Gray male. ------+--------+-------+-----------+--------------+-------+-----------

SERIES B.

+--------+-------+-----------+--------------+-------+----------- 239 | 935 | 363 | |Survived |Oats |Gray male. 254 | 975 | 369 | |About 2 days | do. |Gray female. 267 | 1,050 | 342 |50 minutes |1 hour | do. |White. | | | | 4 minutes | | 268 | 1,100 | 363 | |About 3 hours | do. | Do. 419 | 1,600 | 350 |6 hours |Less than | do. |Gray male. | | | | 24 hours | | 420 | 1,250 | 352 |1 hour |2 hours | do. | Do. | | | | 35 minutes | | 421 | 1,485 | 351 |6 hours |Less than | do. | Do. | | | | 24 hours | | 424 | 1,295 | 293 |2 hours |22 hours | do. | White male. 423 | 1,205 | 300 | do. |Less than | do. | Do. | | | | 19 hours | | 422 | 1,440 | 291 | do. |2½ hours | do. | Do. ------+--------+-------+-----------+--------------+-------+------------

INJECTION INTO THE PERITONEAL CAVITY.

In a number of experiments caffein was introduced into the peritoneal cavity. Rabbits of different varieties receiving a diet of oats or carrots were employed for this purpose; food and water were given ad libitum. The minimum doses required to induce symptoms or cause death in these animals were determined; tests with caffein were also made on young rabbits in order to study the influence of age on the resistance to this substance. The results are shown in the following experiments:

SERIES A.

In this series large doses were administered, approximating 0.3 gram per kilo.

_Rabbit 71. Gray female. Weight, 1,659 grams._

January 20: 2.20 p. m., 25 cc aqueous solution 2 per cent caffein (300 mg per kilo) were injected into the peritoneal cavity; 3.45 p. m., when doors of cage were opened rabbit had spasm of short duration.

January 21: Rabbit found dead.

_Rabbit 72. Gray and white. Weight, 1,402 grams._

January 21: 11.17 a. m., 20.2 cc (aqueous solution) of 2 per cent caffein (300 mg per kilo) injected into peritoneal cavity from burette; 11.25 a. m., paralysis; 11.30 a. m., rabbit had convulsion when picked up from the floor, followed by several spasms later; 11.35 a. m., typical tetanus; 12.30 noon, found dead.

_Rabbit 61. Black female. Weight, 2,143 grams._

January 19: 40 cc 2 per cent caffein, aqueous solution (300 mg per kilo), injected into peritoneal cavity from burette; tetanus when about 30 cc were injected; when removed from holder, repeated and violent convulsions, terminating in death.

SERIES B.

The object of these experiments was to determine the minimum lethal dose; 0.2 to 0.15 gram of caffein per kilo was injected into the rabbits of this series.

_Rabbit 69. White female. Weight, 1,714 grams._

January 20: 10.15 a. m., 6 cc 2 per cent caffein, aqueous solution, injected into peritoneal cavity. No symptoms, under observation for 45 minutes, rabbit defecated rather copiously; feces were soft; 11 a. m., 6 cc 2 per cent caffein, aqueous solution, injected into peritoneal cavity, no symptoms, under observation for 40 minutes; 11.40, 6 cc 2 per cent caffein injected into peritoneal cavity; 11.45, rabbit is restless, reflexes increased.

_Rabbit 70. Gray and white female. Weight, 1,487 grams._

January 20: 1.30 p. m., 15 cc 2 per cent aqueous solution of caffein (0.2 gram per kilo) injected into the peritoneal cavity; 2.20 p. m., no symptoms.

January 30: About 2 p. m. rabbit died.

February 1: _Autopsy_: Cirrhosis of the liver; enteritis of small intestines; stomach and kidneys normal.

_Rabbit 93. Maltese, male. Weight, 1,197 grams._

March 2: 11.30 a. m., 12 cc of 2 per cent caffein (200 mg per kilo) injected into peritoneal cavity; 11.35 a. m., while being released from holder, tetanus occurred, repeated attacks later, clonic convulsions with tonic rigidity of posterior extremities during the attacks as well as during intervals, anterior extremities were relaxed during the intervals between the attacks, opisthotonos of cervical region but kyphosis in lumbar region were observed, no salivation nor dilatation of the pupils; 2 p. m., rabbit died.

_Rabbit 92. Yellow female. Weight, 1,388 grams._

February 25, 4.15 p. m., 14 cc 2 per cent caffein (0.2 gram per kilo) injected into peritoneal cavity; 4.20 p. m., restlessness and increased reflexes, rabbit found stretched out in cage, but raised himself on his legs again; 4.45, general tremor when touched.

February 26: 9 a. m., rabbit found dead. _Autopsy_: Hemorrhage into abdominal muscles at site of injection; hemorrhage also in walls of stomach opposite similar spot in abdominal wall.

_Rabbit 309. Belgian hare, female. Weight, 1,500 grams. Diet, oats._

March 2: 2.05 p. m., 2 per cent caffein solution (0.2 gram per kilo) injected into peritoneal cavity; 2.25 p. m., found dead, no urine found in bladder.

_Rabbit 307. Belgian hare, female. Weight, 1,320 grams. Diet, oats._

March 2: 12 noon, urine obtained from bladder, clear amber colored, no albumin, no reduction; 12.06 p. m., 10 cc of 2 per cent caffein (0.151 gram per kilo) injected into peritoneal cavity; 1.30 p. m., rabbit placed on floor, runs around but anterior and posterior extremities soon extended, in tonic condition; 2.25 p. m., reflexes increased, paralysis of extremities, dyspnoea; 4.50 p. m., about 100 cc urine collected, no albumin, reduction of Fehling's solution moderate.

March 3: 9.30 a. m., posterior extremities extended and rigid, anterior extremities paralyzed, respiration less frequent and deeper than normal. Rabbit died at 11.50 a. m.; urine collected since 4.50 p. m. previous day gave very heavy reduction of Fehling's solution. _Autopsy_: Animal in good condition; in the left axillary region was observed a hemorrhage into the subcutaneous and muscular tissue of that region. The ventral portion of the large colon, in contact with the ventral abdominal wall, showed a hemorrhagic area about one-half inch in length, such as might be produced by a puncture or bruise of the colon through the abdominal wall. A small portion of the small intestine adjacent to the colon was affected in a similar manner. All internal organs were apparently normal.

_Rabbit 308. Belgian hare, female. Weight, 1,350 grams. Diet, oats._

March 2: 11.45 a. m., urine obtained from bladder, no albumen, no reduction; 11.50 a. m., 10 cc 2 per cent caffein (0.15 gram per kilo) injected into peritoneal cavity; 1.30 p. m., not very active, no abnormal symptoms otherwise; 3.30 p. m., rabbit looked depressed, made very little attempt to move about, remained in one position most of the time when placed on floor; 4.30 p. m., 180 cc urine collected, no albumen, reduction of Fehling's solution moderate.

March 3: 9.30 a. m., rabbit looks normal, is able to walk but is easily fatigued when made to walk about or when placed on his side, followed by paralysis of anterior extremities, posterior extremities apparently normal, about 90 cc of urine collected at noon was free from albumen, did not reduce Fehling's solution.

March 4: 11 a. m., lying on his side in cage, anterior extremities limp, posterior extremities extended and rigid, is in dying condition.

March 5: 9 a. m., found dead. _Autopsy_: Liver engorged; spleen congested, but not enlarged; kidneys, some congestion in cortex; stomach filled, mucosa thickened and easily pulled off; petechial hemorrhages on serosa of colon.

SERIES C.

The experiments of this series were made to determine the minimum toxic dose.

_Rabbit 295. Belgian hare, female. Weight, 1,205 grams. Diet, carrots._

March 1: 10.40 a. m., 6 cc 2 per cent caffein (0.1 gram per kilo) injected into peritoneal cavity; about 2 cc of urine obtained before injecting caffein; 2 p. m. 100 cc urine, bloody in appearance, collected, a moderate quantity of albumen present, no reduction; 3.40 p. m., no symptoms.

March 4: 2 p. m., rabbit looks well.

_Rabbit 293. Belgian hare, female. Weight, 1,605 grams. Diet, carrots._

March 1: Urine from bladder clear, alkaline; 11.55 a. m., 8 cc 2 per cent caffein (0.1 gram per kilo) injected into peritoneal cavity; 3 p. m., 90 cc urine normal in color collected, no albumen, no reduction; 3.40 p. m., no symptoms.

March 4: 1.15 p. m., rabbit looks normal.

_Rabbit 292. Belgian hare, male. Weight, 1,595 grams. Diet, carrots._

March 1: 10.10 a. m., 8 cc 2 per cent caffein (0.1 gram per kilo) solution injected into peritoneal cavity; 10.40 a. m., rabbit urinated, reflexes increased, but no other symptoms; 10.50 a. m., no urine obtained from bladder; 2 p. m., 105 cc of clear pale urine collected; no albumen, no reduction; 3.40 p. m., no symptoms.

March 4: 2 p. m., rabbit looks well, urine collected, did not contain sugar.

_Rabbit 298. Belgian hare, female. Weight, 1,205 grams. Diet, carrots._

March 1: 4.06 p. m., 7.5 cc 2 per cent caffein solution (0.125 gram per kilo) injected into peritoneal cavity, urine obtained from bladder immediately after injection, no albumen, no reduction; 5.30 p. m., reflexes increased, rabbit was able to run around, but became paralyzed soon; 5.40 p. m., rabbit is again able to run around.

March 3: 10 a. m., anterior extremities paralyzed, is able to use posterior extremities.

March 4: 1 p. m., rabbit looks normal.

_Rabbit 223. Belgian hare, male. Weight, 1,165 grams. Diet, carrots._

March 1: 3.50 p. m., urine obtained from bladder clear, amber colored, no albumen, no sugar; 3.52 p. m., 7.5 cc 2 per cent caffein (125 mg per kilo) injected into peritoneal cavity; 5.40 p. m., rabbit makes little attempt to run when put on the floor, weakness of extremities marked.

March 4: 1.15 p. m., rabbit normal.

SERIES D.

The object of the experiments of this series was to study the effect of age on the resistance to caffein. Half-grown rabbits were, therefore, used in the following experiments.

_Rabbit 310. Belgian hare, female. Weight, 880 grams. Diet, oats._

March 2: 3.25 p. m., 9 cc 2 per cent caffein (0.2 gram per kilo) injected into peritoneal cavity.

March 3: 9.30 a. m., no symptoms, rabbit looks normal.

March 4: 11 a. m., posterior extremities abducted, walked when placed on the floor, made no attempt to change attitude when placed on its side, remained some time in this position.

March 5: 9 a. m., found dead. _Autopsy_: Liver showed areas of degeneration; kidneys congestion and petechial hemorrhage on cortex; small and large intestines, inflammation marked; bladder distended.

_Rabbit 75. Gray and white, female. Weight, 842 grams._

January 25: 3 p. m., 8.5 cc 2 per cent caffein solution (0.2 gram per kilo) injected into peritoneal cavity; 3.15 p. m., anterior extremities weak and reflexes increased.

January 27: Rabbit paralyzed but is able to turn over when placed on back.

_Rabbit 74. Gray and white, female. Weight, 692 grams._