42 The Intralobular Framework of the Human Spleen 



the fibrils encircle the venules and anastomose with one another to 

 form a series of circular and spiral rings completely surrounding the 

 Imnen. The}' are an integral part of the framework of the pulp cords, 

 modified only as to their distribution. Encircling and limiting the 

 venous spaces the spirals are not compactly apposed to one another, but 

 separated by intervening spaces of varying width. They are identical 

 with the fibrils first described by Henle as white fibrous tissue and by 

 more recent writers as elastic fibers. The nature of the fibril per se 

 will be discussed below. 



In fortunate preparations the intralobular framework may be seen 

 to extend throughout the Malpigliian follicle and become continuous 

 with the coats of the afferent artery. (Fig. 1, E.) The fibrils are 

 much more delicate and fewer in number than those of the pulp cords. 

 The meshes are larger and the network is uninterrupted by the spaces 

 representing the capillary veins. There is no membrane or condensa- 

 tion of the framework at the periphery of the follicle to mark it off 

 from the surrounding portion of the lobule, the only transition being 

 from the coarser to the more delicate network. 



In all their reactions the component fibrils correspond to reticulum 

 as described by Mall. They differ from elastic fibrils in that they are 

 not digested with pancreatin ferment and are resistant to weak acids 

 and alkalies. Unlike white fibrils, they continually branch and anasto- 

 mose. Their reaction with pancreatin is constant, and in specimens 

 subjected to the enzyme for forty-eight hours the framework remains 

 intact where sufficiently protected from mechanical injury. The fibrils 

 within the Malpighian follicles, because of their extreme delicacy, are 

 easily broken away in the process of washing, and in a majority of 

 specimens this portion of the framework is wanting. In fortunate 

 preparations, however, this framework is present, intact, after the 

 continued action of the enzyme. 



The staining reaction of these fibrils is intermediate between that of 

 elastic and white fibrous tissue. By prolonging the time of staining or 

 by heating, reticulum fibrils may be tinted and in cases somewhat 

 deeply stained by the so-called specific elastic tissue stains of Weigert, 

 Mallory and Unna-Tanzer. Sections of human spleen from which all 

 elastic tissue has been removed by digesting forty-eight hours in pan- 

 creatin, may be tinted a deep purple by staining two hours in Weigert's 

 elastic tissue stain. By continuing the staining for three hours at 38° 

 C. the intensity of the color is much increased. The reaction is not 

 the same as that with elastic fibrils, the intense black color never being 

 attained with reticulum as with elastic tissue. Likewise with the orcein 



