ADIPOSE SUBSTANCES. 785 



absorbing those accumulations ; concluding their journeys across 

 the desert with the special stores of fat much reduced. Simi- 

 larly, in other Mammals, when the digestive function and ap- 

 petite are in abeyance, as in disease, or when food is withheld 

 or scarce, the general fat is absorbed f to support the actions of 

 the machine.' 1 Hence the need of accumulations of this nutritive 

 material in torpid mammals prior to their falling into that state, 

 as in Marmots, Hedgehogs, c. The subcutaneous fat, which 

 forms a thick layer in October, becomes thin in March, yet 

 remains after the fat of the abdomen, mesentery, and about the 

 kidneys has quite disappeared; suggesting, as Jenner remarks, 

 that the external fat also serves as a defence against cold. 2 The 

 subcutaneous wrap of blubber in the naked Cetacea, serves as the 

 non-conductor of heat, in place of hair. 



In Physeter portions of spermaceti occur in the general subcu- 

 taneous blubber, but the main bulk is stored in the vast supra- 

 cranial basin, in cells of areolar tissue, strengthened by aponeu- 

 rotic partitions. The purest spermaceti lies in the smallest and 

 most delicate cells : it is the stearic constituent in excess which 

 crystallises on cooling. For economic purposes these masses are 

 separated by pressure in woollen bags from the elaine, then 

 washed with a weak solution of caustic potash, melted in boiling 

 water, and strained. Thus prepared for commerce spermaceti 

 appears as semi-transparent brittle masses of a foliate fracture, 

 soapy to the touch, with a slight odour and greasy taste : its 

 specific gravity is '943 ; it fuses at about 114 ; thep urified cry- 

 stalline scales deposited from a solution in boiling alcohol, form 

 ( cetine.' From the blubber of species of Delphinus a peculiar 

 fatty principle called ' phocenine ' is obtained. The characteristic 

 colour of goats' fat is associated with a principle called ( hircin.' 



With ordinary stearine a variable proportion of ( margarine ' 

 is always combined, and both these and * elaine ' are compounds 

 of a distinct fatty acid with the sweet principle called ( glycerine.' 



xx. vol. iii. p. 213. 2 Ib. p. 216. 



VOL. III. 3 E 



