General Anatomy, Applied to Physiology and Medicine, Vol. 3 (of 3)

by Xavier Bichat

I shall not speak of the tendency of the dermis to combine with tannin, nor of the phenomena of this combination; I should only be able to repeat what others have said upon this point. I will merely remark that it would be very important to try the effects of tannin on the large sub-cutaneous aponeuroses, the texture of which being essentially gelatinous has much analogy with that of the dermis, and which from their extent and delicacy might serve for uses to which the dermoid texture when tanned is less adapted. We know that the tanned skin is no longer what it was in the natural state, and that the substance with which it is then penetrated gives it an artificial consistence. If much tannin has been combined with it, it loses entirely the faculty of acquiring the horny hardness, and becomes brittle; whilst if but little of this substance is added to it, it preserves in part its suppleness and the property of crisping from the action of caloric. I would compare tanned skin to bone penetrated with the phosphate of lime, and that which is not tanned, to the cartilaginous parenchyma from which the acids have removed this phosphate.

II. Parts common to the Organization of the Dermoid System. Cellular Texture.

The whole dermis is penetrated with a large quantity of this texture. It is arranged in the following way; from the exterior of the sub-cutaneous cellular layer, an infinite number of elongations is detached which penetrate the contiguous spaces of the chorion, enter afterwards into those which are more exterior, and finally terminate in the numerous pores which transmit outwards the vessels, the nerves and the hairs, which have previously passed through this cellular texture. We can then consider the chorion as a kind of sponge, the spaces of which represent the interstices, and which the cellular texture penetrates on all sides; so that if it was possible to separate by dissection, these spaces from the cellular texture, and the organs which are in it, there would be a kind of sieve pierced in all directions. Art cannot arrive at it but with difficulty on account of the delicacy of the parts; but that which is not done by dissection, nature often effects. In biles I have observed that all that which fills the interstices of the dermoid fibres disappears by suppuration, and that these fibres, separated besides by the swelling of the parts, exhibit truly the appearance of a sieve of which I have just spoken, when the fluid that moistens them is removed. The bile differs in fact from many other cutaneous eruptions, in this that it attacks the cellular texture of the spaces of the chorion, whilst they have their seat, as I have said, in the reticular body. I do not know any acute affection which attacks the chorion itself; all have their seat either on its surface, or in the cellular texture of its cells. Its dense and compact texture seems, like that of the aponeuroses, not able to be changed until a length of time. In elephantiasis I have seen this texture evidently disorganized.

M. Thillaye showed me portions of skin taken from a cemetery, in which every thing that filled the dermoid spaces had disappeared, and in which these spaces and their dried fibres formed a real membranous sponge through which the light could everywhere be seen. In this case the reverse of what is seen in long continued macerations had taken place, in which the fatty cellular texture, changed into a solid, white substance, preserves, as I have said, the form of the spaces which it filled, whilst the dermoid fibres reduced to the pulpy state, are easily removed. In the first case it is the mould only which is left; in the second it is the substance which is contained in it.

In chronic leucophlegmasia, the sub-cutaneous serum gradually extends along the cellular elongations of the spaces of the dermis, separates their fibres, consequently enlarges these spaces, and sometimes penetrates even to the epidermis, which it breaks in different places, and through the crevices of which it escapes. In this case, there is not resolution of the skin into cellular texture, as it is called, but a separation of the dermoid fibres, which always remain.

I do not presume that the cellular texture of the chorion extends to its external surface, under the epidermis; for when this has been removed, fleshy granulations are not formed, now, in all the parts where the cellular texture is found, these granulations are produced, when the parts are laid bare.

Blood Vessels.

The arteries winding in the sub-cutaneous cellular texture, furnish an infinite number of small branches which are introduced with the cellular parcels into the most internal dermoid spaces, afterwards pass into those that are nearer, approximate by winding and anastomosing a thousand times through the spaces of the external surface of the chorion, finally go through the pores of this surface, and give rise to that external capillary net-work of which we have spoken in the article upon the reticular body, and to which in the ordinary state but very little red blood comes. In this course through the dermoid spaces, but few small arteries remain in the fibres of the chorion itself, as fine injections prove. These fibres resemble in this respect those of the aponeuroses through which many vessels pass, but which have but few belonging to their own texture.

The veins follow nearly the motion of the arteries, but in an inverse direction. After having passed through the dermoid spaces and the cellular texture which fills them, they go to the great sub-cutaneous trunks, which run a long course, form, as we have seen, a system wholly distinct by its position from that of the arteries and which can be often traced through the integuments. Not seen in the natural state, the venous ramifications of the spaces of the chorion are considerably dilated in the subjacent cancerous tumours, and make the skin which covers these tumours appear to be marked with blue lines, which always grow larger as the tumour increases. Whenever there is a considerable distention of the cutaneous organ by an aneurism, pregnancy, dropsy, &c. this dilatation also takes place, provided the cause of the distention pursues a chronic course; for nothing similar is seen in acute affections, whatever swellings may have taken place, as in those consequent upon fractures, upon compound luxations, &c.

All the black blood formed in the skin goes into the general venous system; no portion belongs to the abdominal.