CHAP XXXIV.] 



MALPIGHIAN TUFTS. 



493 



of the tuft in the parrot and in the boa, is less than in any other 

 instance recorded ; and in these animals, as is well known, the 

 urine is almost solid. It is especially worthy of remark, that the 

 uriniferous tubes do not exhibit a corresponding difference in 

 dimensions. 



Table of the Diameter of Malpighian Bodies, and of the Tubes emerging from 

 them, in Fractions of an English Inch. 



The small efferent vessel from 

 the Malpighian tuft passes at 

 once into the plexus round the 

 tubes, and, as it lies between the 

 capillary plexus of the tuft, 

 on the one hand, and that sur- 

 rounding the tubes upon the 

 other, it bears the same rela- 

 tion to these two capillary sys- 

 tems as the portal vein bears 

 to those of the intestinal canal 

 and the liver; hence these 

 efferent vessels may be re- 

 garded as analogous to a 

 portal system of vessels. This 

 view is further strengthened by 

 an examination of the arrange- 

 ment of the vessels in the kid- 

 ney of the boa constrictor, figs, 

 239, 240. In this animal, the 

 blood, after passing through 



Plan of the arrangement of the elements of a lobe of 

 the kidney in the boa constrictor. The references are 

 the same as in fig. 240. 



