146 SPECIAL HISTOLOGY. 



terspaces between the larger trabecule and the coarser vessels, 

 and is so soft as to be readily removed from a fragment of the 

 organ. It consists of three elements; viz., of the most delicate 

 blood-vessels of the spleen, of microscopic fibres . and trabecules, 



The walls of the capillaries are exceedingly delicate and often indistinguishable as 

 distinct structures. Both the longitudinal inner coat and the transverse muscular 

 coat of the arterioles are very well developed in Man. 



3. Structure of the " contents" of the Malpighian follicles. — We have been unable 

 to find either cavity or fluid in the contents of the Malpighian follicles. So far as 

 we have seen, they are solid bodies — their outer portion or " wall" being constituted 

 as above described; while the inner is, to use the accurate phraseology of Mr. 

 Wharton Jones, composed of " nucleated granular corpuscles and nucleated cells, 

 similar to those of the red substance, cohering together in a mass by means of a 

 diffluent intercellular substance, and, interspersed among these, a few somewhat 

 larger nucleated cells" (1. c, p. 35). 



The idea that the Malpighian corpuscles were hollow bodies originated with 

 Malpighi himself; but Miiller, in opposition to him and to Rudplphi, asserts very 

 justly that in the Pig, Sheep, and Ox, they are firm and resistant. 



From all that has been said, it results very clearly that the only difference between 

 the " pulp" and the " Malpighian follicles" of the spleen is one of degree, consisting 

 in the greater or less development of the vascular network and the greater or less 

 amount of metamorphosis, which the elements of the parenchyma have undergone. 

 It is, furthermore, sufficiently obvious that the anatomical differences between a 

 solitary follicle of the intestine, a Peyer's patch, a lymphatic gland and a spleen, are 

 also questions of degree. It is impossible to distinguish, under the microscope, a 

 minute lymphatic gland — such as may be met with in the mesentery of the Rat, for 

 example — from one of the follicles of the Peyer's patches of the same animal. But 

 as the intestinal follicles are aggregated to form the Peyer's patches, so the lymphatic 

 follicles are aggregated to form the large lymphatic glands : increase the vascularity 

 of the stroma of a lymphatic gland and we have a spleen. 



On the other hand, we can state decidedly that the follicles of the tonsils, both in 

 Man and in the Sheep, are traversed abundantly by capillaries, so that they come 

 under the same category; differing, however, from the lymphatic glands and spleen, 

 in that the follicles are arranged, not in solid masses, but around diverticula of the 

 intestinal mucous membrane, which, in the tonsils (both in Man and in the Sheep), 

 take the form of more or less irregularly ramified ducts. Starting, therefore, from the 

 simple intestinal follicle, we have two series of vascular glands — the one, the solid 

 series, reaching its utmost complexity in the spleen (and perhaps the supra-renal 

 bodies and thymus) ; the other, the diverticular series. Does the latter, however, 

 reach its highest complication in the tonsils ? or rather do not these lead in the 

 plainest way to the liver, which is, like them, essentially a solid meshwork of capil- 

 laries, filled by indifferent tissue and arranged around a complex diverticulum of the 

 intestine ? It appears to us that the structure of the tonsils affords, in this way, an 

 analogical basis for the views of Dr. Handfield Jones ; and tends greatly to support 

 the doctrine that the liver is essentially one of the vascular glands. While adding 

 the liver, however, we should exclude the thyroid ; its structure being totally 

 different from that of the rest of the class. — Eds.] 



