CHAP. VII.] THE CONNECTIVE TISSUES. 259 



It is impossible to study these analyses without concluding that, 

 though agreeing in general chemical reactions, the mucin-like con- 

 stituent of the tissues of invertebrates is a different substance 

 from the rnucin obtained from mucous membranes. 



Products of When boiled for twenty or twenty-five minutes 



decomposi- with dilute sulphuric acid, mucin is decomposed with 

 tion of mucm. ^ Q f orma tion of acid albumin and a body possessing 

 the property of reducing salts of copper and bismuth similar to 

 those of glucose. That this body is not a sugar is proved by the facts 

 that it does not rotate polarized light, and that it is incapable of 

 alcoholic fermentation; it appears to be a nitrogenous body 1 . 



When boiled with strong sulphuric acid for seven hours mucin 

 yields leucine and tyrosine (Obolensky). 



When boiled with caustic soda, on neutralizing and shaking 

 with ether, the latter fluid dissolves a body which possesses the 

 reaction of pyrocatechin (0 6 H 6 2 ), i.e. is coloured of an emerald 

 green colour by solution of ferric chloride (Obolensky). 



The products obtained when mucin is subjected to the action of 

 pancreatic ferment, prolonged until putrefaction sets in, have been 

 studied under Nencki's direction by Walchli 2 ; amongst them were 

 found ammonia, indol, a large quantity of butyric acid, and a substance 

 possessed of a sweet taste and reducing copper salts. 



Relations Mucin is unquestionably a product of the differentia- 



of mucin. tion of the protoplasm of certain animal cells, and is 



obviously derived from the proteids. It is conceivable that it may 

 result from a decomposition in which both collagen and mucin origin- 

 ate; what the nature of the decomposition may be is, however, quite 

 unknown. 



SECT. 2. ADIPOSE TISSUE. 



structural ^ a * occ urs in the animal body either in a state 



Elements of of solution or minute suspension in its juices, or 

 Adipose deposited within the interior of cells. This is espe- 



cially the case in cells which are developed in, and 

 supported by, the connective-tissue of certain regions ; these cells, 

 which originally are identical with connective-tissue cells, undergo 

 changes which ultimately result in the diminution of the cell proto- 

 plasm (at the expense of which, or through the agency of which* 

 oily matter is deposited within the cell) and in the development of a 

 well-marked cell- wall which serves to contain their oily contents. These 

 oily contents undergo remarkable fluctuations according to the state 

 of nutrition of the animal. 



Fat cells are usually found in groups or clusters, supported by 

 the fibrous elements of connective tissue, and surrounded by a network 



1 Obolensky, "Ueber Mucin aus der Submaxillardriise. " Pfliiger's Archiv, Vol. iv. 

 p. 336. 



2 Walchli, Ber. d. deutschen chem. Gesellsch. xi. 1878, p. 509. 



172 



