242 ANDREW JACKSON HOWE. 



more delightful than any that my eyes had ever beheld ; for here 

 I discovered more than fifty circulations of the blood in different 

 places. I saw not only the blood in many places was conveyed 

 through exceedingly minute vessels, from the middle of the tail 

 toward the edges, but that each of these vessels had a curve or 

 turning, and carried the blood back toward the middle of the 

 tail, in order to be conveyed to the heart. Hereby it appeared 

 plainly to me that the blood-vessels I now saw in this animal, and 

 which bear the names of arteries and veins, are, in fact, one and 

 the same that is to say, they are properly termed arteries as long 

 as they convey the blood to the farthest extremities of the ves- 

 sels, and veins when they bring it back toward the heart." 



While the observations of Leeuwenhock are to 

 be trusted in the main, the modern histologist does 

 not entirely agree with him. A capillary is not an 

 arterial nor venous radicle, but an intermediate vessel 

 peculiarly constructed in its parieties for the endos- 

 motic transmission of nutriment ; it is the seat of 

 assimilation. A capillary tube in a vascular sense, is 

 not impervious like a pellicle of caoutchouc, nor is it 

 a mere strainer, but the meshes of its walls are cel- 

 lular and possess the power to convert nutriment 

 into structure, the new material becoming like the 

 original. For instance, muscle would have imparted 

 to it by its capillaries such material as may prove 

 nourishment for muscle ; a gland would get such a 

 substance as might increase gland structure ; and 

 brain obtains food for brain, and the draft is made 

 from one and the same kind of supplies, yet trans- 

 muted by the cellular capillary walls into just such 

 structure as may be in need of nutritious supplies. 

 Furthermore, the capillaries in the different animals 

 impart to the flesh of each creature its peculiar odor, 

 flavor, texture, etc. If a pig, or a dog, or a cat, eat 

 for dinner just what a man does, the food is digested 

 in much the same way in all, and carried into the 



