THE SPLEEN. 557 



between the larger trabeculse 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 bloodvessels of the spleen, of 

 microscopic fibres and trabecula^ and of peculiar cells of the parenchyma. 

 In Man and in Animals the occurrence of extra vasated blood, in manifold 

 stages of metamorphosis, is so frequent, that it may be almost regarded 

 as a normal constituent. According to its amount and to the disten- 

 sion of the bloodvessels, the pulp appears sometimes of a brighter/some- 

 times of a darker blood-red ; besides which, however, it must be noted 

 that the pulp has also its own proper red coloring matter. 



The fibres of the pulp are of two kinds. Firstly, there are microscopic 

 trabeculce, answering completely to those visible with the naked eye and 

 possessing the same structure, except that in many Mammals they con- 

 tain more smooth muscles, or are even entirely composed of them. As 

 a general rule, their diameter varies between O'OOo and O'Ol of a line; 

 in quantity they differ in different animals and in different parts of the 

 spleen. In Man I find them to be more rare and broader than in other 



while the inner is, to use the accurate phraseologyof Mr. Wharton Jones, composed, of " nu- 

 cleated granular corpuscles and nucleated cells, similar to those of the red substance, coher- 

 ing 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 Rudolphi, 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 metamor- 

 phosis, which the elements of the parenchyma have undergone. It is, furthermore, suffi- 

 ciently 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 impos- 

 sible to distinguish, under the microscope, a minute lymphatic 1 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 

 IVyer'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 irregu- 

 larly 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 mesh- 

 work of capillaries, 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 ana- 

 logical 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. TRS.] 



