ADIPOSE TISSUE. 



59 



of each granule, and disintegrating the granules 

 by the contraction of chemical agency. The 

 borders of these granules appear by refracted 

 light a little fringed an effect which M. lias- 

 pail attributes to the corrosive action of the 

 nitric acid. 



When magnified to 100 diameters, they ap- 

 pear like irregular hexaedral or pentaedral 

 bodies, from two to four lines in diameter, and 

 all accurately fitted or conjoined to each other. 

 The actual diameter of these granules in the 

 adult human subject varies according to Ras- 

 pail from .00117 to .00562 of an English inch. 

 In youth and infancy they are stated to be still 

 smaller. 



The chief point to bear in remembrance is 

 that the adipose tissue consists of two distinct 

 parts, one a vital organic and secreting part, 

 the other an inorganic and secreted product, 

 which is void of vital principle. The chemical 

 constitution of fat has been investigated by 

 Chevreul, Braconnot, and more recently by 

 M. Raspail. According to the researches of 

 M. Chevreul fat consists essentially of two 

 proximate principles, stearine (crraa^, sebum, 

 sapo,j and elaine, (eAatov, oleum.) ,The former 

 is a solid substance, colourless, tasteless, and 

 almost inodorous, soluble in alcohol, and pre- 

 serving its solidity at a temperature of 176 

 Fahrenheit. Elaine, on the contrary, though 

 colourless, or at most of a yellow tint, and 

 lighter than water, is fluid at a temperature of 

 from 63 to 65 Fahrenheit, and is greatly 

 more soluble in alcohol. To the presence of 

 stearine in a large proportion, the intra-serous 

 sebaceous fat owes its solidity and firmness ; 

 whereas the elasticity and softness of the sub- 

 cutaneous adipose tissue, and the marrow, 

 depend upon the predominance of elaine. 



It is farther important to attend to the ele- 

 mentary composition of fat. Each variety of 

 fat consists of carbon, hydrogen, and oxygen ; 

 and a few, as hog's lard, blubber, nut oil, and 

 almond oil, contain a small trace of azote. 

 The proportion of the carbon is greatest and 

 varies in general from 7-10ths to 4-5ths of the 

 whole. The proportion of hydrogen varies 

 from l-10th to 1-5 th. That of oxygen varies 

 from four or five parts in the hundred to 

 12 and 13. It appears, therefore, that fat and 

 each of its constituent principles are a highly 

 carbonaceous animal substance. 



Little doubt can be entertained that animal 

 fat is the result of a process of secretion. But 

 it is no easy matter to determine the mode in 

 which this is effected. Previous to the time 

 of Malpighi it was a very general opinion that 

 the blood exuding from the vessels was con- 

 verted into adipose matter. This fancy was 

 refuted by Malpighi, who, departing, however, 

 from strict observation, imagined a set of ducts, 

 (ductus adiposi) issuing from glands, in which 

 he conceived the fat to be elaborated and pre- 

 pared. To this fancy he appears to have been 

 led by his study of the lymphatic glands, and 

 inability to comprehend how the process of 

 secretion could be accomplished by arteries 

 only. The doctrine, though embraced by 

 Perrault, Collins, and Hartsoecher, was over- 



thrown by the strong arguments which Ruysch 

 deduced from his injections; and Malpighi 

 afterwards acknowledged its weakness and re- 

 nounced it. In short, neither the glands nor 

 the ducts of the adipose membrane have ever 

 been seen, unless we admit the testimony of 

 the Members of the Parisian Academy, who 

 state that they saw them in the civet cat, and 

 to this we must oppose the fact that Morgagni, 

 by anatomical evidence, disproved their ex- 

 istence. Winslow, though willing to adopt the 

 notion of Malpighi, admits, nevertheless, that 

 the particular organ, by which the fat is sepa- 

 rated from the blood, is unknown. Haller, 

 on the contrary, aware of the permeability of 

 the arteries, and inferring from the phenomena 

 of injections either of watery liquors or melted 

 tallow, their direct communication with the 

 cells of the adipose tissue, and trusting to the 

 testimony of Malpighi, Ruysch, Glisson, and 

 Morgagni, that fat exists in the arterial blood, 

 saw no difficulty in the doctrine of secretion, 

 or rather of a process of separation ; and upon 

 much the same grounds is this opinion adopted 

 by Portal. Bichat, again, contends that no fat 

 can be recognized in the arterial blood, and 

 justly adduces the fact, that none can be dis- 

 tinguished in blood drawn from the temporal 

 artery. To the accuracy of this fact I can 

 bear direct testimony, having repeatedly ex- 

 amined with the view of recognizing the buffy 

 coat, and detecting oily particles, blood, which 

 I had drawn from this vessel, the latter sub- 

 stance invariably without success. In wounds 

 in the human body during life, and living 

 animals, oily particles may be seen floating on 

 the surface of the blood ; but these, it may be 

 said, proceed from the division of the adipose 

 vesicles; and hence it has been inferred that 

 the arterial blood contains no adipose or olea- 

 ginous matter. 



It may be doubted, however, whether facts 

 of this kind are adequate to prove whether 

 adipose or oily matter does not naturally exist 

 in the blood, and both from the experiments 

 of Chevreul, and those of Lecanu and Boudet 

 it appears that small quantities of adipose or 

 puriloid matter may be obtained from this 

 fluid. M. Chevreul, for example, shows that 

 fatty matter may be obtained from the fibrine 

 of arterial blood ; and from a series of elabo- 

 rate and accurate experiments, estimates the 

 quantity of fatty matter in fibrine at from four 

 to five per cent.* Lecanu and Boudet have 

 also recently shown that crystals of pearly- 

 coloured matter having the characters of an 

 adipose substance exist in, and may be ob- 

 tained in small proportion from the serum of 

 the blood .f These inferences apply, according 

 to the authors, to blood in its healthy state. 



In certain states of the system the blood 

 drawn from the veins has presented serum of 

 an opaque or milky appearance, and which 

 has been proved to depend on the presence of 

 adipose or oleaginous matter. Thus, indepen- 

 dent of opaque or milky serum noticed by 



* Journal de Physiol. torn. iv. p. 119. 

 t Journal de Pharmacie, 1830-33. 



