On the Relations between the „Islets of Langerhans" etc. 67 



the ox are of the more solid form (the second of the two varieties 

 described in the dog), and contain more nuclei in a given area than 

 do the corresponding structures in the dog. There are, however, some 

 islets of the alveolar form. 



Transition forms between islet and zymogenous tissue are common 

 (PI. V, fig. 6, trans, c). 



In tlie pancreas of the carnivorous animals reference lias been 

 made to individual elements or small groups of cells which stain very 

 deeply with all ordinary stains. These are particularly well seen in 

 specimens fixed in Fleniming's fluid and stained with iron-haematoxylin 

 (Pi. IV, figs 1 and 2), In the ox these cells are still more commonly 

 present and the darkly staining tissue presents itself in three forms. 

 1. Individual cells scattered through the zymogenous tissue, sharply 

 differentiated from their neighbours by their intense reaction to all 

 ordinary stains (PI. V, fig. 6, hath. c). 2. Small accumulations of such 

 cells consisting of two, three, up to about six elements usually occupying 

 the blind extremity of an alveolus (PI. V, fig. 6, bath, c,).^) 2. Larger 

 masses of darkly staining cells, comparable in size to the lightly 

 staining islets of Langerhans (PI. V, fig. 6, hath. t.). The two kinds 

 of tissue may sometimes be seen side by side (PI. V, fig. 6, hath. t. 

 and Ujjt. t.). 



In treating of the islets of lower vertebrates it will be seen that 

 these two kinds of tissue aie regularly present in addition to the 

 ordinary zymogenous tissue. We propose the name „bathychrome" 

 for the darkly staining material and the name „leptochrome" for the 

 lightly staining tissue. Thus the known islets of Langerhans consist 

 of leptochrome tissue, while the separate, scattered, deeply stained cells 

 in the zymogenous tissue, and the dark islet depicted in the ox 

 (PI. V, fig. 6, hath, t.) consist of bathy chrome. Further reference to 

 these different kinds of tissue will be made below. 



The islets of Langerhans in the rahhit. 



From our observations we have been unable to confirm Dale's 



^) On renewed examination of our ox specimens we find that these larger 

 darkly-staining masses are not constant, and we are not inclined to attach the same 

 importance to them as was formerly the case. [Note added Jan. 1. 1907.] 



