STUDIES ON THE PANCREAS OF THE GUINEA PIG 343 



These methods have brought to light in the pancreas of the 

 guinea pig a system of tubules which also have escaped the injec- 

 tion methods, and which appear to be of considerable importance 

 by reason of their relation to the growth of pancreatic tissue. 

 This is a system of fine tubules which, by forming anastomoses, 

 connect together adjacent sections of the duct and neighboring 

 branches of the duct. 



This system was studied to some extent by Gianelli ('98) and 

 by Laguesse, the former regarding them as constituting a sort of 

 embryonic tissue endowed with the function of furnishing new 

 pancreatic acini. By the majority of observers they have been 

 confused with the system of glands attached to the ducts. 



As shown in my preparations made by means of pyronin or 

 methylene blue, this system is composed of a series of tubules of 

 small calibre, which take their origin from the duct or from the 

 larger branches of the duct, and which branch freely in the con- 

 nective tissue surrounding these ducts. The branches anastomose 

 freely with one another (fig. 4), and so form, along the main duct 

 and its primary branches, a web of extreme intricacy, binding 

 together the successive sections of the duct, and also connecting 

 primary and secondary branches with one another, even at some 

 distance from the main duct. From this branchyig system come 

 off many short branches which end blindly. 



The tubules of which this system is composed vary from 12-27 

 micra in diameter, though they may be thicker than this at cer- 

 tain points where small islets are attached, or where a mucous 

 gland takes its origin from the tubule. In some cases the tubules 

 take the form of a highly branched tubular gland (fig. 5). The 

 usual arrangement is well shown in fig. 4, although the course of 

 the tubules is in reality much more tortuous than in the figure, 

 which is made from a preparation in which the tissues are stretched 

 to make the preparation thinner and more transparent. The 

 small projections seen at intervals along the tubules are chiefly 

 mucous glands, though some are small islets of Langerhans 



The number of these tubules varies in different guinea pigs, 

 and at different parts of the gland. In some guinea pigs the whole 

 duct may be surrounded by a web of such tubules, some originat- 



