102 ABSORPTION BY THE BLOOD-VESSELS. 



regarded as complete in the human embryo of two months old. After 

 that time "blood-cells are generated upon the second plan, from the chyle 

 corpuscles alone. 



It is a significant circumstance that this transition from the reproduc- 

 tive to the non-reproductive blood-cell is coincident usually with the dis- 

 appearance of the external branchia3, or the closing of the branchial fis- 

 sures. There can be no question that the destined function of the per- 

 fect blood-cell is the introduction of oxygen to the system. In their or- 

 igin and in their object they are therefore in relation with the respiratory 

 mechanism. 



CHAPTER VI. 



ABSOKPTION BY THE BLOOD-VESSELS. 



Proof of Absorption by the Blood Capillaries. Occurs as a physical Necessity. Nature of Cap- 

 illary Attraction. Its Phenomena in the Rise and Depression of Liquids. Conditions for 

 producing a Flow in a Capillary Tube. Passage of Liquids through minute Pores. General 

 Propositions respecting Capillary Attraction. Endosmosis and Exosmosis. They depend on 

 Capillary Attraction. Force against which these Movements may take place. Illustrations of 

 selecting Power. General View of the entire Function of Absorption, lacteal and venous. 



THAT the blood-vessels of the stomach and intestinal tube participate 

 Substances are in the function of absorption is demonstrated by many dif- 

 the^bbodX- ferent facts * Medicaments placed in the stomach after its 

 iiiaries. pyloric orifice has been tied will produce their specific effect 



almost as rapidly as under natural circumstances ; and, since there are 

 no proper lacteals upon that organ, and its lymphatics seem to be inade- 

 quate, the absorption of these agents can have taken place through the 

 blood-vessels only. 



This conclusion is substantiated by an examination of the blood of 

 the gastric and mesenteric veins. It varies with the 'stage of diges- 

 tion and the nature of the food. At first there is a general lowering of 

 the percentage amount of the solid ingredients, this being evidently the 

 result of the absorption of water. At a more advanced period, the rela- 

 tive proportion of albumen, or rather of albuminose, rises, and along with 

 it the extractive, gelatine, and sugar increase. As with the chyle in the 

 lacteals, so with the blood in the mesenteric veins, coagulation takes 

 place imperfectly, or perhaps not at all. It is stated that the mesen- 

 teric blood of a fasting animal does not differ from the ordinary venous 

 blood. 



The position of the blood-vessels, both on the mucous surface of the 

 stomach and particularly on the villi of the intestine, is favorable to the 



