TISSUES OF THE BODY. 



ISO 



In 1000 of coagulum of the chyle : 

 Water, . . . 887 '6 

 Fibrin, . . .39'0 

 Free fat, . . . 1*5 

 Fatty acids of the soaps, 0'3 

 Albumen . . . ") 

 Sugar and other organic > 66*0 



matters, . . ) 



Haematin, . . 2'1 



Mineral constituents ) 



without iron, . j 



5-5 



In 1000 of serum of ditto : 

 Water, . . . 958*5 

 Fibrin, 



Free fat, . . . 0'5 



Fatty acids of the soaps, 

 Albumen, 

 Sugar and other organic ) 



matters, . . j 

 Hsernatin, 

 Mineral constituents 



without iron, . 



0-3 

 30-9 



2-3 



7-5 



As yet we know but little as to the first appearance of lymph-cells in 

 the embryo. But from the fact alone, that lymph-corpuscles may be 

 observed in foetal blood at an early period, we may infer that they occur 

 also largely in the lymph. 



REMARKS. London, Edinburgh, and Dublii 

 Comp. also Nasse's article "Chyle," p. 235. 



Philosophical Magazine, Feb. 1841. 



B. Tissues composed of simple cells, with a small amount 

 of solid intermediate substance. 



3. Epithelium. 

 86. 



By epithelium we understand a tissue formed of closely associated 

 cells, which clothes, in layers of greater or less thickness, the external and 

 internal surface of the body, canals of exit and even numerous com- 

 pletely closed cavities of the system. It is only through the nearer 

 acquaintance with the history of its development that we have been 

 enlightened as to its true nature. And for this we are indebted to the 

 searching investigations of Remak, from which we learn Jihat at an early 

 period of development the flat rudimentary embryo is bounded above 

 and below by two strata of cells, the corneous and intestinal glandular 

 layers. From the first of these the epithelium of the external surface 

 takes its origin, and from the second that of the digestive tract. But the 

 cells of these two layers play a further part in the construction of 

 numerous' other organs. 



Thus we find that it is not alone the outer clothing of the body, the 

 skin, with its manifold reduplications, which bears these epithelial layers 

 of cells, but the mucous membrane also with which it is continuous, 

 the glands of the intestinal tube, the internal surfaces of the respiratory 

 and generative apparatus, and even parts which have completely ceased 

 to communicate with these primordial epithelial layers ; as, for instance, 

 the cavities in the brain, the spaces and bounding surfaces in the eye 

 and auditory, organs: these all possess this characteristic covering. Owing 

 to the fact that the secreting gland-cells having the same origin as 

 the epithelia, we frequently find transitions from one kind of cell into the 

 other in the interior of those organs. 



The epithelium extends, however, still further throughout the body. 

 The strata of cells enclosed between the corneous and intestinal glandular 

 layers, namely, the so-called middle or intermediate layer, becomes, with 



