non-vascular Animal Tissues. 161 



puseles, 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 which 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. 

 In considering the first class, he commences with articular cartilage, 

 which he describes at great length in the various stages of its de- 

 velopment, and at the different periods of life. He gives in detail 

 the account of numerous dissections of the ovum and foetus illustrating 

 the first stage, during which he shows that no blood-vessels enter 

 into the substance of any of the textures composing a joint ; but 

 that the changes its component parts undergo, are effected by the 

 nutrient fluid from the large blood-vessels, by which, at this stage, 

 each articulation is surrounded. In the second stage of the develop- 

 ment of articular cartilage, the author shows, by numerous dissec- 

 tions, the process by which the blood-vessels are extended into the 

 substance of the epiphysal cartilage, and converge towards the at- 

 tached surface of articular cartilage, and how, at the same time, 

 blood-vessels are equally prolonged over a certain portion of its free 

 surface. He shows that none of these blood-vessels enter the sub- 

 stance of the articular cartilage, and he points out that in them the 

 arteries become continuous with the veins ; first, by their terminating 

 in a single vessel, from which the veins arise ; secondly, by their 

 forming large dilatations from which the veins originate ; and, lastly, 

 they become directly continuous with the veins in the formation of 

 loops of various characters. In the third stage, that which is exhi. 

 bited in adult life, the epiphysal cartilage is converted into osseous 

 cancelli. These contain large blood-vessels, which are separated 

 from the articular cartilage by a layer of bone composed of corpus- 

 cles, and the author believes that the principal source of nutrition to 

 this tissue is the nutrient fluid which exudes into it from these 

 vessels, by passing through the articular lamella just noticed. The 

 free surface of adult articular cartilage is nourished by vessels which 

 pass to a slight extent over it. The author points out the presence 

 of fine tubes which pervade the attached portion of adult articular 

 cartilage, to which he ascribes the function of transmitting through 

 its substance the nutritive fluid derived from the vessels of the can- 

 celli. He also advances the opinion that the articular cartilage be- 

 comes thinner during the whole of life, by being gradually converted 

 into bone. 



Fibro-cartilage constitutes the second tissue of the first class. 

 The author first enters upon an examination of its structure ; and in 

 order to arrive at some definite conclusions on this subject, whereon 

 anatomists of all ages have so much differed, he made numerous 



Phil. Mag. S. 3. Vol. 19. No. 122. Aug. 1841. M 



