10 PHYSIOLOGY AT THE FARM. 



being poured into the duodenum, contributes to the prepara- 

 tion of the true nutriment for absorption ; and, secondly, as 

 producing ulterior changes on whatever part of that nutriment 

 afterwards comes to be transmitted through its substance along 

 with the blood of the portal vein. The venous blood of the liver, 

 derived chiefly from the ramifications of the portal vein in the 

 substance of the liver, passes almost immediately to the right 

 side of the heart, and the venous blood of the veins in the fore 

 part of the chest, with which the chyle from the lacteal system 

 is mingled, passes, by a course in no great degree longer, to 

 the same side of the heart. Thus the venous blood, which re- 

 ceives the nutriment by the two channels just indicated, is 

 brought at once to that side of the heart whence the blood is 

 transmitted through the lungs. In the lungs the nutriment, 

 after new changes, is finally incorporated with the blood as it 

 passes from the venous to the arterial state, whence the arte- 

 rial blood arrives at the left side of the heart, reinforced by sup- 

 plies of fresh material, to be distributed by the arterial system 

 of vessels all over the body, to renovate the solids and secre- 

 tions concerned in the never-ceasing offices of life. 



Such are the two obvious modes in which the constitution 

 of the blood is maintained. There is, however, another kind 

 of sanguification highly probable, yet still somewhat obscure, 

 and therefore rather conjectural than certain. It seems not 

 unlikely that the blood itself affords germs separated from it 

 within certain organs, called of late vascular or blood glands, 

 and that these germs grow into corpuscles or globular cells, at 

 the cost of the proteine compounds contained in the lympha- 

 tics with which such vascular or blood glands are abundantly 

 supplied ; and that such corpuscles, being conveyed into the 

 vascular system in part, if not wholly, by the lymphatic trunks, 

 constitute the white corpuscles of the blood, out of which the 

 red corpuscles of the blood are finally developed. Among such 



