334 THE URINO-GENITAL SYSTEM, THE ADRENALS, ETC. 



I have seen two twigs passing to the same corpuscle; as a rule, 

 however, each Malpighian corpuscle receives only one twig. A more 

 general arrangement is that the artery courses nearer the ventral 

 surface and in a more winding course, several twigs are then given 

 off close together, from the convex surface of one of the curves, and 

 these course to their respective corpuscles. 



In the Malpighian corpuscle the arterial twig forms a series of 

 loops and then passes out to open abruptly into one of the branches 

 of the neighbouring venous anastomosis (Hyrtl). 



(2) [The Malpighian corpuscles and their capsules (Figs. 216 I, 

 218 III). The corpuscles lie nearer the ventral than the dorsal 

 surface. They are rounded oval bodies, formed of loops of an 

 arterial twig, held together by a small amount of connective-tissue. 

 Each corpuscle is enclosed in a capsule, which it incompletely fills 

 (Fig. 217)1. 



The capsules are formed of connective-tissue and lined with a 

 flattened epithelium (Fig. 2 1 8 III) : according to Duncan the fibrous 

 coat is arranged in two layers (III a). Towards the opening of tlie 

 uriniferous tube the epithelium increases in thickness. 



According to Hyrtl, the corpuscles are arranged in two layers, a 

 more superficial one and a deeper one ; and are of two sizes, the 

 larger being as a rule the more superficial (ventral).] 



(]) [The uriniferous tubes (Figs. 217 and 218). Each tube 

 originates at a narrow opening on the dorsal surface of a Mal- 

 pighian capsule. The tube gradually widens and is lined with 

 a short rounded or cubical epithelium (Roth), (Fig. 218 III); each 

 epithelial cell bearing a small number of extremely small cilia (Bow- 

 man, KoUiker, Duncan, and others). The cilia of the cells nearest 

 the capsule are directed towards it (Heidenhain), those of the cells 

 further away have an opposite direction (Spengel). This portion of 

 the tube is known as the neck ; it courses dorsal wards. 



The second portion of the tube {Tubvlns con fori us), (Fig. 218 

 III, IX, and XII) has a very tortuous course in the dorsal part 

 of the kidney, and then winds towards the ventral surface. This 

 portion is lined with columnar epithelium, which has granular 

 contents, and possesses large distinct nuclei. The cells of this part 



1 8ee Plate IT. 

 Portions of two transverse vertical sections through the kidney. — G. H. 

 1. Kidney of llaim esculmta, partial injection of the uriniferous tubes with silver nitrate 



(Hartnack, Oc. I, Syst. 7). 

 II. Kidney of Jiana lemporaria, stained witli borax-carmine (Hartnack. Oc. 1, Svi-t. 7). 



