78 K. MITSUKURT. 



large vein is seen to enter each suprarenal at its posterior end, 

 which is a branch of the renal vein in the case of the left, 

 and of the vena cava inferior in the right suprarenal. On 

 cutting open a fresh suprarenal, in a median longitudinal 

 plane, its division into whitish-yellow cortical part and 

 greyish medullary part becomes at once obvious. The 

 former exhibits also a subdivision into three more or less 

 distinct layers. Starting from the outside, they are (1) a 

 rather thin greyish layer ; (2) yellowish layer comprising 

 the main mass of the organ, and showing, even to the naked 

 eye, radial striation ; and (3) a layer, of a much darker 

 yellow, adjoining to the medullary substance. These layers 

 are for the most part arranged concentrically ; but at the 

 posterior end there is a modification in their relations, which, 

 singularly enough, seems to have hitherto escaped observa- 

 tion. The medullary substance, instead of being covered 

 by the cortical layers, as in other parts, here becomes 

 attenuated into a narrow streak, and reaches the outside. 

 Roughly speaking, therefore, the cortical substance is in the 

 shape of a horseshoe, completely surrounding the medullary 

 part, except at one point at the posterior end. The histo- 

 logical structure of this part is of great interest, as will be 

 seen further on, on account of the peculiar developmental 

 history of the medullary substance. A section of the supra- 

 renal body across its shorter diameter will show three layers 

 in concentric rings. 



Fig. 1 shows a part of a transverse section of the supra- 

 renal considerably magjiified. If the whole section had been 

 figured the outline would be oval, and the medullary sub- 

 stance (m), of which only a small portion is represented, 

 would occupy a rather large irregularly oval area in the 

 centre. In the figure, however, are shown all three parts 

 of which the suprarenal is composed, viz. (1) the outer cap- 

 sule of connective tissue (d), (2) the cortical substance 

 {a, b, c), and (3) the medullary substance (m). I shall 

 briefly describe each of these three portions. 



Of the connective tissue capsules I need only say that 

 nerves and blood-vessels are found embedded in it in toler- 

 able abundance, and that bundles of connective-tissue fibres 

 from the capsule are sent inwards to form the framework 

 of the whole organ. 



The whole space between the outer capsule and the medul- 

 lary part is occupied by the cortical substance, which, there- 

 fore, constitutes the main mass of the organ. Briefly speaking, 

 it is made up of large cells, supported in a very fine network 

 of connective tissue — so fine that each cell has its own cavity 



