88 INTRODUCTION OF FAT. 



digested matter ; that they become turgid with chyle, and have a diame- 

 ter of about the yJ^- of an inch ; that, as they select material, they 

 throw it into the lacteal tube, either by bursting or deliquescing, and at 

 the same time set free broods of germs from which new cells are developed. 

 So far, therefore, as their duration is concerned, if this be their true histo- 

 ry, they are even more transitory than the corresponding cells of plants. 



That the lacteals are connected with respiratory digestion seems to be 

 Fat is intro- plainly indicated by the circumstances of their occurrence, 

 facteais Into 6 ^ one ^ them are found upon the stomach, nor even on that 

 the blood. part of the duodenum which is above the entrance of the he- 

 patic and pancreatic ducts, but below that point they are scattered in pro- 

 fusion all over the small intestine. The digestion of fatty bodies not 

 taking place until the food has gained the duodenum, vessels for the ab- 

 sorption of the emulsions to which that digestion gives rise are not re- 

 quired until after that point is passed. Correctly speaking, however, 

 the lacteals are only lymphatics which are taking up oil presented to 

 them. In view of the use which the oils subserve in the animal economy, 

 the lacteals are in reality an appendix to the respiratory system. There 

 can be no doubt that through their channel oils and fats, under the form of 

 emulsions, are transmitted to the blood. The analysis of the chyle shows 

 that it is always rich in fat, and, indeed, it is supposed by some physi- 

 ologists that the objects just described. as cells, surrounding the origin of 

 the lacteals, are nothing more than oil or fat globules accumulated there 

 and waiting to be taken up, or that the disappearance and exuviation of 

 the so-called cells is an optical deception, due to their walls becoming 

 permeated with oil. 



The manner in which oil globules collect round the villus I have re- 

 marked as being very strikingly displayed 

 in the case of the gray squirrel after feed- 

 ing on fatty nuts. As shown in Fig. 28, 

 the whole structure looks as if it were dis- 

 tended with oil globules, a a, in the midst 

 of which the origin of the lacteal, b b b, may 

 be doubtfully and dimly discerned. 



Although it can not be admitted that the 

 Evolution and production and deliquescence 



function of the / .1 n c MV i Half-diagram of villi of the gray squirrel 



cells of the * " ie Ce -" S * ^"" 1S a demon- after feeding on nuts. 



villi. strated fact, and that on this the action of the lacteals as ab- 



sorbent vessels for the most part depends, the rapid evolution and disap- 

 pearance of these cells is by no means a physiological impossibility. Bot- 

 anists assert that, in a single night, the Bo vista giganteum, a puff-ball, 

 can develop from a mere point to such a size that it must contain fifty 

 thousand millions of cells a number that seems almost incredible. The 



