Part 11

Now will appear the third ventricle in the posterior part; and it is hard, for it gives rise to the greater part of the motive nerves which are of a strong and firm nature. This ventricle is pyramidal in shape, and culminates in an apex directed upwards where images of visible things (_spetie_) are conserved, for these are better stored in a strait than in an ample space; but the part below is wide to receive these images, which are better received in an ample than in a strait place. This ventricle has two functions: it gives rise to the spinal cord [_nucha_, an Arabian term] and motor nerves; and it is also the storehouse of the _memorative_ faculties.

From what [has been said] it will be apparent that when the back of the head is injured, the memory immediately suffers; when the middle part is injured, the estimative and cognitive faculties suffer; and when the anterior part is injured, the faculties of common sensation and of imagination (_fantasia_) suffer. And thus it is that the doctors have become aware of the location of these powers.

This being disposed of, thou wilt next raise the brain carefully so as not to break the nerves. Commencing now with the part in front, there will first appear two small fleshy protuberances like two nipples, of like substance to the brain in which they originate, and covered by a thin membrane, the pia mater. These are the olfactory organs, wherein is the sense of smell.

From the brain arise seven pairs of nerves. Proceed therefore farther with the anterior part, and thou wilt see the first pair of these nerves, which are large, and called the _nervi optici_. These have their origin in the front ventricle of the brain and proceed towards the eyes. But before they pass through the pia mater, they join together, and at their place of union there is a perforated spot. Galen maintains that these nerves only join or rather unite, but do not intersect, so that the nerve that comes from the right after union returns again towards the right, and similarly with the nerve coming from the left, which after the union returns towards the left eye.[185] But Rhazes maintains the contrary,[186] although the opinion of Galen is the more common. These nerves are subservient to sight, and they are united so that the images of the things received by the two eyes and conveyed by the two nerves should return in unity; so that one thing should not appear as two.

After these two nerves, raise the brain towards its middle and thou wilt see another pair of nerves, thin and firm, which also go to the eyes, to give them voluntary movement, controlling certain muscles.

Farther on thou wilt see the third pair of nerves, one part of which goes to the face to give it sensation and voluntary movement, while another part goes to give taste to the tongue. Yet a third part of these nerves mingles with the fourth[187] pair of nerves, and together they descend to give sensation to the diaphragm, stomach, and other viscera. A certain part also of the fourth[187] pair of nerves goes to give sensation to the palate.

Then there is the fifth pair of nerves [which] go to the _petrous_ bone around the ear; and of these nerves there are framed in the ear-holes certain membranes, which are the organs of hearing.

Next there is the sixth pair of nerves, which divides into three parts. One part goes to the muscles of the throat, the second to the muscles of the shoulders, and the third and largest descends to the epiglottis and to the diaphragm, and spreads into the chest, the heart, and the lungs, accompanying the nerves of the third pair. From the nerves of this sixth pair which go to the epiglottis arise the nerves of the voice, called _reversive_.

The seventh pair of nerves arise at the back of the brain and give voluntary movement to the tongue.

Of these seven pairs of nerves, the first two pairs originate in the anterior part of the brain, the third pair originates between the anterior and posterior parts, while the remaining four pairs originate in the posterior part.

Proceeding still farther, the brain may be completely raised, and the eighth part of the head will appear, that is, the two membranes situated below the brain. When these in turn are raised there will appear the ninth part, which is a certain net called _rethe mirabile_, because it is composed of exceedingly strong and marvellous texture, augmented by certain very fine arteries which are branches of arteries that ascend from the heart, and are called the _apoplectic arteries_. In these arteries of this net is contained the vital spirit, sent from the heart to be changed to animal spirit. That the spirit may be the better modified and distributed, nature made these arteries very fine, and separated them into very small branches so that the spirit should be minutely divided. Nature placed the rethe mirabile under the brain because it was necessary to guard its site carefully, and also that the moist vapours of the brain which fall upon the net, obstructing it, should induce natural sleep.

After all these things thou wilt see the basal bone which is the tenth and last part of the head, and called _basilar_, because it is the base and foundation of the whole head; and it was made hard so that the superfluities which descend to it should not putrefy it. This bone can be seen to be formed of many other bones articulated together. It is divisible into the petrous bones and the bones of the nose and eyes and two other lateral bones which can only be seen by means of disarticulation. [Folio 10 verso, line 22.]

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The ten parts or layers of the head are a commonplace of the anatomy of the period, taken from Avicenna. We may illustrate the division by the crude contemporary diagram of Fig. 11, which is improved in the later drawing reproduced in Fig. 12.

Manfredi’s account of the brain itself is amplified from Mondino. The division of this organ into three ventricles, each associated with a corresponding division of the mental functions, was very familiar to medical writers of the fifteenth century. The idea is found among Western writers as early as St. Augustine (354-430), and is encountered in the writings of Roger Bacon (1214-94). It had long been popularized in mediaeval psychology by the writings of Albertus Magnus (1206-80). The anatomical distinction is found in Haly Abbas, Avicenna, and Rhazes, and in some of the best MSS. of the latter writer a rough diagram of the ventricles is given.[188] These writers are all clearly indebted to the anatomy of Galen,[189] but on the psychological side Albertus Magnus probably drew mainly either from Ghazali[190] (1059-1111), who in turn derived his inspiration from Nemesius (fourth century) and Johannes Damascenus (died 756), or else from early writers of the Salernitan tradition, such as Constantine[191] (eleventh century), or Petrocello[192] (twelfth century), who drew largely on Theophilus (seventh century).[193]

This outline of a tripartite division of the brain and its cavities was closely followed throughout the Middle Ages, as was also the curiously naïve and excessively ‘materialistic’ psychology to which it gave rise, and which Manfredi adopts. We illustrate his views of the relationship of the different parts of the brain and their parallelism in mental processes, from a series of diagrams extracted from contemporary works (Figs. 13-18).

The brain was regarded by mediaeval and early Renaissance anatomists as having two channels of discharge through which the _phlegm_, the especial product of this organ, could be evacuated when in excess. One of these channels communicated with the anterior ventricle of the brain and poured its secretion into the nose. It may be identified with the _anterior colature_ or cribriform plate. The second, the _lacuna_, led down from the second ventricle and poured its secretion into the pharynx. It may be identified with the infundibulum, pituitary body, and ‘cella turcica’. The term ‘pituitary’ which we still use is derived from its supposed association with the ‘pituita’ or phlegm. At an early date this process was connected with the four humours (Fig. 14). The rest of the description of the brain can be easily followed. The comparison of the choroid plexus to a worm is very common. The suggestion originated with Galen and was developed by the Arabians.

COMPARATIVE TABLE OF ANCIENT AND MODERN NOMENCLATURE OF CRANIAL NERVES.

_Mondino and Manfredi following Galen, | especially in the_ περὶ χρείας τω̑ν ἐν | _Modern usage._ ἀνθρώπου σώματι μορίων. _De usu partium | corporis humani._ | ---------------------------------------+---------------------------- Not regarded as separate nerves. | I. Olfactory nerves. ---------------------------------------+---------------------------- I. τὰ μαλακὰ νευ̑ρα τω̑ν ὀφθαλμω̑ν. | II. Optic nerves. ---------------------------------------+---------------------------- II. τὰ κινητικὰ τω̑ν ἀμφ᾽ αὐτοὺς μυω̑ν. | III. Oculomotor nerves. ---------------------------------------+---------------------------- Not mentioned. | IV. Trochlear nerves. ---------------------------------------+---------------------------- III. τρίτη συζυγία. } | V. Trigeminal nerves. IV. τετάρτη συζυγία. } | Mondino and Manfredi confuse | Galen’s fourth pair and Galen’s | sixth pair. | ---------------------------------------+---------------------------- Not mentioned by Manfredi. By | VI. Abducent nerves. Galen probably united with II. | ---------------------------------------+---------------------------- V. πέεμπτη συζυγία. |{ VII. Facial nerves. |{VIII. Auditory nerves. ---------------------------------------+---------------------------- VI. ἕκτη συζυγία. | {IX. Glossopharyngeal | nerves. | { X. Vagi. | {XI. Accessory nerves of | Willis. ---------------------------------------+---------------------------- VII. ἑβδόμη συζυγία. | XII. Hypoglossal nerves. ---------------------------------------+----------------------------

The nomenclature of the cranial nerves adopted by Manfredi is taken from Mondino and is almost identical with that of Galen, whose classification is summarized above.[194] Manfredi’s description of Galen’s fourth pair is confused and inadequate, but his account of Galen’s sixth pair is an improvement upon Mondino.

The ‘rete mirabile’ is an interesting survival of Galenic anatomy. This structure is hardly present in man, but is developed in the lower animals, and especially in calves, upon whose bodies Galen worked. The father of physiology regarded the ‘rete mirabile’ as the place where the psychic pneuma was elaborated.[195] Galen’s findings in the lower animals were assiduously transferred to the human body, to which his descriptions are much less applicable, while his views on the pneuma lasted in more or less misunderstood form well into the seventeenth century.

(_b_) THE EYE

Tractate i, Chapter 3

(folio 11 recto) The socket of the eye is not over-depressed, for it has to receive the images (_spetie_) of visible things. Nor does it project greatly, lest it should be liable to injury from exterior violence. For the eyes of man being very soft and susceptible, nature provided eyebrows as a shield above, and eyelids as protectors in front, and made moreover the projections of the maxillae and the nose, so that the eyes should be guarded on every side. So great was the solicitude of nature for these members.

Seven are the tunics of the eye and three its humours. Three front coatings join with three coatings at the back like six shields, the edges of every pair joining each to each, the outer being larger and containing the others. The seventh tunic is largest of all, and encloses the whole eye, and therefore it is called _conjunctiva_ because it joins and surrounds the whole eye except the place where the pupil is, and that small part [is covered] by the cornea. Now this first tunic where it covers the outside part is seen to be white.

The second tunic in its front part is called _cornea_ because it resembles horn in its substance and colour; and this covering is transparent, so that the images of visible things may penetrate through it. And it is also solid and large and composed of four membranes, so that being near external things it should not receive hurt. With this [corneal tunic] is united posteriorly another tunic [the third] called _sclerotic_, i.e. hard. These two coverings have their origin in the membrane about the brain, that is in the dura mater, just as the first tunic arises from the membrane over the skull, called _almochatim_.

The fourth tunic as to its front part is called _uvea_ [because] it is like a seed of a black grape, and in its midst is a hole called the pupil. Nature made this tunic opaque so that the visual spirit should be conserved and not dissipated by the light outside. Moreover nature made the opening in the tunic that the image might penetrate freely; while it is narrow, so that the visual spirit should be concentrated. Thus when the said pupil, or rather hole, dilates more than usual, either naturally or accidentally, the sight becomes imperfect. [The uveal tunic] joins posteriorly the fifth tunic, called _secundina_ because it is made like the after-birth, i.e. the membrane in which the child is enveloped in its mother’s womb, and it arises from the pia mater.

The sixth coating in front is called _arachnoid_ because it is formed after the manner of a spider’s web, and posteriorly it joins the seventh coating, called _retina_, because it is made like a net.

Between the uvea and the arachnoid anteriorly there is a humour called _albugineus_, like the white of an egg, to moisten the eye and to preserve the convexity of the cornea. In a dead man this humour dries up, and the cornea falls and is flattened, and then the vulgar say that there appears a curtain before the eyes which is an infallible sign of death. Also this humour holds the pupil open; therefore when it dries up the pupil contracts.

Between the two last tunics, i.e. the arachnoid and the retina, which have their origin from the optic nerve, there are two humours. These are the _vitreous_ humour, so called from its likeness to liquified glass, and the _crystalline_ humour, from its likeness to a crystal. This is also called the _grandid_, because it is like a hailstone; and it is somewhat hard and round, but flattened anteriorly where it receives the images of visible things, and posteriorly pyramidal shape and pointed. And here is completed the act of seeing. In the posterior part it is surrounded by the vitreous humours by which it is nourished. The crystalline humour is convex anteriorly and the vitreous posteriorly. And the optic nerves come to the eyes and convey the images seen by the eyes to [the seat of] common sensation and to the other internal faculties. [Folio 12 verso, line 7.]

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A great deal of attention was paid by the Arabians to the diseases and the structure of the eye, and the essentials of Manfredi’s description are to be found in Rhazes, Hunain ben Ishak, and Haly Abbas. The tradition presented by these writers passed early into Western science, and is reproduced, for example, in the works of Constantine Africanus and in the well-known anatomy to which the name of Richardus Anglicus (Richard of Wendover) has become attached[197] (cp. Fig. 19). Avicenna’s description of the eye is somewhat different, and gave rise to the tradition reproduced in the works of John of Peckham and of Roger Bacon (Plate XXXVIII _a_), and it influenced the views of Leonardo and even perhaps of Vesalius (Fig. 20). The views on the anatomy of the eye expressed by Rhazes, Hunain ben Ishak, and Haly Abbas were, on the whole, more widely accepted than those of Avicenna.

The treatment of the eye was always felt to be hardly within the range of the ordinary practitioner of surgery, and its structure, as we learn from Guy de Chauliac,[198] was not usually treated in the general course of anatomy. The custom was rather to refer the student to special works such as those of Jesu Aly or of Alcoatim.

Manfredi’s description of the anatomy of the eye is that generally accepted at the end of the fifteenth and the beginning of the sixteenth centuries, and is unusually clear for its date. It represents a considerable advance on such writers as Henri de Mondeville (1260-1320)[199] or the pseudo Richardus Anglicus, and is far superior to the descriptions of the eye dating from the fourteenth and fifteenth centuries recently brought to light by Sudhoff.[200] We reproduce as illustrating Manfredi a diagram taken from the _Margarita philosophica_ of Gregorius Reisch (died 1525). This represents the earliest printed figure of any value of the anatomy of the eye (Fig. 19).[201] We give for comparison the figure from a thirteenth-century MS. of Roger Bacon (Plate XXXVIII _a_), representing the rival tradition of Avicenna and Alhazen that influenced Leonardo da Vinci and other contemporaries of Manfredi. These figures may be compared with that of Vesalius (1543, Fig. 20), whose description of the eye is less free from traditional bias than are most parts of his epoch-making work.

In reading any early description of the eye, it is to be remembered that until the nineteenth century the ‘emanation theory’ prevailed. Light was regarded as of the nature of a stream of particles emitted from the object seen, and the act of vision was considered as a collision of this emanation with an emission of something from the eye itself, called in mediaeval writings the ‘visual spirit’.

(_c_) THE HEART

Tractate ii, Chapter 3

(folio 19 verso) Then you will see in the midst of the lung the heart, covered by its membranes. [It is thus situated] that the air attracted by this lung should cool it, and that thus the heat and spirit of the heart be tempered. This member is the most important of the four [principal members], because it is the first to live and the last to die. It is of medium size compared with the other members of man, but compared with the hearts of other animals it is very large, because man, in a quantitative and not an intensive sense, has more natural heat than other animals. It is pyramidal, that is in the form of a flame; because it is of excellent warmth, therefore it is necessary that it should be of a shape resembling a flame. Its figure is also called ‘pine-shaped’, because it is wide below and narrow above, being thus formed that distinction could better be made between its cavities or ventricles; moreover, had it been made of a shape all uniform as is the lower part, it would be too heavy and ponderous.

This member is situated in the middle of the entire body, measured in every direction; that is, in the middle between the upper and lower parts: in the middle also between front and back and right and left, like a king standing in the midst of his kingdom, and this was done that it might give the strength of life equally to all the members; and although the heart as regards its foundation and base be in the middle, yet its point declines to the left below the left breast, so that it warms the left side as the liver warms the right.

This member is sustained and strengthened by a certain cartilaginous bone. For since it is continually moving, it needs some point of purchase to support it in its movements. Moreover, it has a certain fatty layer on the outside which prevents the heart from drying and keeps it moist: and there are certain veins and arteries dispersed through its substance: and it is formed also of a kind of hard flesh so that it may sustain many and forceful movements; also it is formed of longitudinal, latitudinal, and transverse fibres, so that it may have the power to attract, retain, and expel.

This member has three ventricles or chambers, like the brain. One ventricle is on the right side, the second on the left, and the third in between. The right ventricle towards the liver has two orifices. One is towards the liver and is very large. Into this there enters a vein called _vena chilis_, which arises in the convexity of the liver and brings the blood from the liver to the heart. In that right ventricle the blood is purified, and then sent by the heart to all the other members.

Now since the heart attracts by this orifice of the _vena chilis_ more than it expels, therefore nature ordains that in the moment of contraction when the blood is expelled this orifice closes, and when the heart dilates it opens.

Moreover there are three little valves (_hostiolitti_) or doors opening from without inward, and these valves are not very depressed; so that by this same orifice only part of the purified blood is expelled to the other members, because part goes to the lungs and the remainder forms the vital spirit; therefore nature ordains that these valves do not entirely close. From the _vena chilis_, before it enters the cavity of the heart, there arises another vein, which surrounds the root of the heart; and from it are given off branches which disperse themselves through the substance of the heart, and from the blood of that vein the heart nourishes itself.