at the last Meeting, and entitled, " Researches tending to prove the Non- vascularity of certain Animal Tissues, and to demonstrate the peculiar uniform mode of their Organization and Nutrition." By Joseph Tovnbee, Esq. Comm'unicated bv Sir Benjamin C. Brcdie, Bart., F.R'.S.
In the inti"oduction to this paper, the author first speaks of the process of nutrition in the animal tissues which are pervaded by ramifications of blood-vessels ; pointing out the circumstance, that even in them there is a considerable extent of tissue which is nou- rished without being in contact with blood-vessels. Tlie knowledge of this fact leads us to the study of the process of nutrition in the non-vascular tissues ; which tissues he divides into the three fol- lowing classes ; namely, first, those comprehending articular carti- lage, and the cartilage of the different classes of fibro- cartilage. Under the second head he comprises the cornea, the cr^'StaUine lens, and the vitreous humour; and, under the third, he arranges the epidermoid appendages : viz. the epithelium, the epidermis, nails and claws, hoofs, hair and bristles, feathers, horn and teeth.
The author then proceeds to show that the due action of the organs, into the composition of which these tissues enter, is incom' patible with theu' vascularity'. In proof of the non-existence of blood-vessels in these tissues, he states that he has demonstrated, by means of injections, that the arteries, which previous anatomists had supposed to penetrate into tiieir substance, either as serous vessels, or as red-bloodvessels too minute for injection, actually terminate in veins before reaching them ; he also shows that around these non- vascular tissues there are numerous vascular convolutions, large dilatations and intricate plexuses of blood-vessels, the object of which he believes to be to arrest the progi'ess of the blood, and to allow a large quantity of it to circulate slowly around these tissues, so that its nutrient Hquor may penetrate into and be diffused through them. The author states that all the non-vascular tissues have an analogous structure, and that they are composed of corpuscles, to which he is induced to ascribe the performance of the very important functions in the process of their nutrition, of circulating throughout, and perhaps of changing the nature of the nutrient fluid which is brought by blood-vessels to their circumference. The author then brings forward facts in proof of the active and vital properties of these corpuscles, and concludes his Introduction by stating, that it appears to him, that the only difference in the mode of nutrition between the vascular and the non-vascular tissues is, that in the former, the fluid vrhich nourishes them is derived from the blood that circulates throughout the capillaries contained in their substance : whilst, in the latter, the nutrient fluid exudes into them from the large and dilated vessels that are distributed around them : and that in both classes, the particles of which the tissues are composed derive from this fluid the elements which nourish them.
The author then enters on an examination of the structure and mode of nutrition of the several tissues of each of these three classes.
