OKGANS OF THE BODY. 



437 



Now, the latter, as the reader is already aware, is formed of a very 

 narrow-meshed retiform sustentacular substance, whose interstices are 

 occupied by lymphoid cells. Between these latter, and along the fine 

 bands of the reticulum, we find that the injection (a) passes further into 

 the pulp. If glue have been employed, the mass hardens subsequently 

 in the form of thin but irregularly defined shell-like fragments around the 

 lymp corpuscles of the pulp, broader at one spot than another. The 

 diameter of each stream varies from about 0'0032 to O'OOOO mm., and is 

 of course affected by the amount of force exercised in injection. The 

 great distensibility of the spleen observed during both health and disease, 

 and which is sufficiently known to every one who has devoted any time to 

 its artificial injection, is in a great measure owing to this capacity for 

 dilatation of the intermediate pulp-passages. 



It was the contemplation of such appearances under the microscope 

 which led to the view supported by many recent observers, that there 

 exists in the pulp an intermediate network of very delicate capillaries, 

 bounded by special walls. At the same time, the reticulum of the pulp 

 was erroneously held to be formed of the collapsed canals of this net. 



It is quite obvious that a slowly increasing pressure will fill a larger 

 and larger portion of this system of interstices in the pulp. Thus we see 

 the Malpighian corpuscles encircled by rings of the reticulated passages ; 

 and eventually the matter employed for injection may advance into the 

 more superficial portions of the same, and give rise there to the same 

 appearance of retiform interlacement. 



But, finally, the injection (b) advances from the pulp (fig. 424, a) into 

 the radicals of the veins (c) already known to us from the preceding 

 section. To its progress there 

 are no obstacles, from the fact 

 that the radicles of the veins are 

 nothing else than interstices 

 found in the tissue of the pulp ; 

 and, therefore, enclosed by the 

 same reticulated tissue which 

 had been filled through the 

 capillaries. 



If, for the control of these 

 artificial injections, other natur- 

 ally filled spleens be carefully 

 examined, in which the red blood- 

 cells have been preserved by 

 certain modes of treatment, and 

 the whole hardened, we will observe that at the terminal portions of 

 the capillaries these coloured elements are prolonged in wall-less pas- 

 sages between the lymph corpuscles, and at other points arranged together 

 in similar rows and groups, which coalesce to form the wail-less radicles 

 of the vein's. 



Thus seeing that both artificial and natural injection point to the same 

 conclusions, we may venture to sum up as follows : the blood from the 

 arterial capillaries is emptied into a system of intermediate passages, 

 which are directly bounded by the cells and fibres of the network of the 

 pulp, and from which the smallest venous radicles with their cribriform 

 walls take origin. 



termediate pulp-passages; c, their transition into 

 Je venous mdicles with their imperfec 



