808 THE FORMATION OF FAT. [BOOK n. 



dition however is temporary only, the lymph is subsequently 

 absorbed and the vesicle shrinks. Or again, the cell- substance 

 may shrink round the lessening fat, but at the same time, deposit 

 on its outside a mucin-like material, so that the whole cell remains 

 of the same size. At times, the emptying of the cell, whether by 

 one method or another, is followed by a rejuvenescence of the cell ; 

 the nucleus by division gives rise to several nuclei, and the cell 

 divides into new cells, each of which may, under appropriate 

 conditions, develope again into a fat-cell. 



505. The fat thus lodged in adipose tissue varies somewhat 

 in composition in various animals, but is chiefly composed of olein, 

 palmitin and stearin in varying proportions, with small quantities 

 of the glycerin compounds of such fatty acids as butyric, capronic, 

 caprylic &c., together with a little lecithin and cholesterin. The 

 ' fat ' of one animal, that is the fat thus contained in adipose tissue, 

 differs from the fat of another animal partly by the presence of 

 more or less of one or more of these less abundant fats, but chiefly 

 by the proportion in which the three main fats, olein, palmitin, 

 and stearin, are respectively present in the mixed fat. The melting 

 points of these three fats being different, the melting point of the 

 fat of the body will differ according to the relative proportions in 

 which the three are present. Thus the subcutaneous fat of man 

 melts at from 15 to 22 or higher, the fat round the kidney 

 being firmer and not melting until 25 ; the fat of the dog melts 

 at about 22, that of the goose at about 25, of the ox at about 

 40, and of the sheep at 50, the less resistant fat of the man and 

 dog containing relatively more olein than that of the ox or of the 

 sheep. 



506. When we come to consider the question, By what 

 processes does the fat make its appearance in the fat-cell ? we are 

 brought face to face with much the same kind of problem as that 

 which occupied us in dealing with glycogen. On the one hand we 

 may suppose that the fat is brought to the fat-cell as fat and is in 

 some way taken up by the cell and deposited in the cell-substance 

 with little or no change. On the other hand, we may suppose 

 that the fat is manufactured by the fat-cell in some such way 

 as mucin or pepsin is manufactured by a mucous or a gastric cell, 

 out of and by means of its cell-substance, and that the process 

 of fattening, or of producing fat in fat-cells, consists essentially 

 in feeding and so building up the cell-substance which sub- 

 sequently breaks down into fat, and does not consist merely in 

 bringing fat within reach of the cell. Which of these views is 

 the true one, or how far are both these operations carried on in 

 the animal body? 



In support of the latter view it may be urged that, not only 

 the more complex living substance, but, as we have more than 

 once urged, the simpler proteid constituent of living substance 

 obviously contains what we may call a fatty radicle, so that we 



