John Bruce MacCallum 253 



was exei-ted to fill the anterior tubules, the posterior ones became much 

 dilated and overfilled. On the lateral surface the fluid at a certain 

 point could be seen to run in opposite directions in the tubules on the 

 surface, and in those just beneath these, which will be explained in the 

 study of the entire course of the tubules. Partial injections were found 

 to be very instructive. It was observed that some of the tubules 

 branched soon after leaving the Wolffian duct. In examining thick sec- 

 tions of these injected specimens cleared in creosote, the tubules were 

 seen sometimes to branch just before entering the glomeruli. In this 

 way one tiibule might be in connection with two or more glomeruli. 

 Evidences of anastomosis and the formation of small networks of tubules 

 were also made out. This was seen partictilarly in the region of the 

 of the dorsal border. 



To gain an exact idea of the course which the tubules take in the 

 gland, a wax reconstruction was made according to the method of Born. 

 This well-known method has been described in detail by Bardeen.' 

 Wax plates, 2 mm. thick, and a series of 'sections cut at 10 //. were used. 

 Every other section was reconstructed and controlled by the intervening 

 ones. The magnification was thus 100 diameters. The model is rep- 

 resented in Fig. 8. The course of the tubtile can be made out plainly 

 from its beginning in the ]\Ialpighian body to its termination in the 

 Wolffian duct. The BoAvman's capsule (to use a term usually employed 

 in describing a similar structure in the permanent kidney) narrows down 

 to a fine tube which runs forwards towards the ventral border. Here 

 it turns and follows the lateral surface of the gland to a short distance 

 from the dorsal border, where it turns abruptly on itself, forming a large 

 loop, and returns to the region of the anterior border. Here it becomes 

 somewhat convoluted and then passes over to the region of the dorsal 

 border, where it is again thrown into convolutions. Erom the dorsal 

 border it proceeds around on the lateral surface of the gland to empty 

 into the Wolffian duct. Certain differences in the calibre of the tubule 

 are to be noted. The collecting tubule arising in the capsule of Bow- 

 man is small, and is lined by cubical epithelium. In the region of the 

 lateral surface it passes into a tube many times larger, lined by large 

 columnar epithelial cells containing granular protoplasm. These cells 

 seem to be secretory in character. This large tube forms a complete 

 loop, as shown in Fig. 8, and passes over in the region of the anterior 

 border into a much smaller, somewhat convoluted segment of the tubule. 

 This in turn runs across the stirface of the Malpighian bodies, where 

 it becomes again greater in diameter, to join with another convoluted 



■■^Bardeen: Johns Hopkins Hospital Bulletin, April-May-June, 1901. 



