THE MOTION OF THE OHYLE. 453 



That the food is received into the stomach, there undergoes a change 

 of its consistence, and is then propelled along the intestines, are obvious 

 facts in the animal economy. But a discovery made in the course of 

 the seventeenth century brought into clearer light the sequel of this 

 series of processes, and its connexion with other functions. In the 

 year 1622, Asellius or Aselli 1 discovered certain minute vessels, 

 termed lucteals, which absorb a white liquid (the chyle) from the 

 bowels, and pour it into the blood. These vessels had, in fact, been 

 discovered by Eristratus, in the ancient world, 2 in the time of Ptolemy ; 

 but Aselli was the first modern who attended to them. He described 

 them in a treatise entitled De Vents Lacteis, cum fiyuris elegant issimis, 

 printed at Milan in 1627, the year after the death of the author. The 

 work is remarkable as the first which exhibits colored anatomical figures ; 

 the arteries and veins are represented in red, the lacteals in black. 



Eustachius, 3 at an earlier period, had described (in the horse) the 

 thoracic duct by which the chyle is poured into the subclavian vein, on 

 the right side of the neck. But this description did not excite so much 

 notice as to prevent its being forgotten, and rediscovered in 1550, after 

 the knowledge of the circulation of the blood had given more impor- 

 tance to such a discovery. Up to this time, 4 it had been supposed 

 that the lacteals carried the chyle to the liver, and that the blood was 

 manufactured there. This opinion had prevailed in all the works of 

 the ancients and moderns ; its falsity was discovered by Pecquet, a 

 French physician, and published in 1651, in his New Anatomical Ex 

 periments ; in which are discovered a receptacle of the chyle, un- 

 known till then, and the vessel which conveys it to the subclavian 

 vein. Pecquet himself, and other anatomists, soon connected this 

 discovery with the doctrine, then recently promulgated, of the circu- 

 lation of the blood. In 1665, these vessels, and the lymphatics 

 which are connected with them, were further illustrated by Ruysch 

 in his exhibition of their valves. (Diluddatio valvularum in vasLi 

 lymplialicis et lacteis.) 



Sect. 2. The Consequent Speculations. Hypotheses of Digestion. 



THUS it was shown that aliments taken into the stomach are, by its 

 action, made to produce chyme ; from the chyme, gradually changed 



1 Mayo, Physiology, p. 156. a Cuv. Hist. Sc. p. 50. 



8 Cuv. Hist. p. 34. 4 Ib. p. 365. 



