298 ON THE STRUCTURE OF THE MALPIGHIAN BODIES 



must refer to Remak's very able essay, ' Ueber Pigment-kugel-haltige 

 Zellen,' in Mtiller's ' Archiv.' for 1852, and to Leydig's recent ' Unter- 

 suchungen tiber Fische und Reptilien,' in which ample evidence of the 

 fact will be found ; and my limits oblige me to allude, with equal 

 brevity, to another important doctrine which many recent writers 

 ha\'e maintained, but which is especially enunciated and illustrated 

 by Leydig, namely — that there is no line of demarcation to be drawn 

 between the spleen, the lymphatic glands. Payer's patches, and the 

 glandula; solitarise, the supra-renal capsules, the thymus, and the 

 pituitar)' body, but that these form one great class of glands character- 

 ized essentially by being masses of indifferent tissue contained in 

 vascular plexuses, and which may therefore ^^'ell retain their old name 

 of Vascular Glands. 



The primary form of these is represented by the solitary gland of 

 the alimentary canal, which is nothing but a local hypertrophy of the 

 indifferent element of the connective tissue of the part, and possesses 

 no other capsule than that which necessarily results from its being 

 surrounded by the latter. 



A number of such bodies as these, in contiguity, constitute, if the)- 

 be developed within a mucous membrane, a Payer's patch ; if within 

 the walls of the splenic artery and its ramifications, a spleen ; if within 

 the walls of lymphatics, a lymphatic gland ; if in the neighbourhood 

 or within the substance (as in Fishes) of the kidney, a supra-rena 

 body ; if in relation with a part of the brain, a pituitary body.^ All 

 these organs agree in possessing nothing that can be called a duct. 

 To those, however, which are in relation with mucous membranes, 

 Kolliker has alread}' justl)' shown (' Handbuch ' and ' Mikr. Anat.') 

 that the ' follicular ' glands of the root of the tongue and the tonsils 

 must be added ; the former of which possess rudimentary, and the 

 latter a tolerably perfect, system of ducts, formed by diverticula of 

 the mucous membrane, around which the elements of the vascular 

 gland are arranged, though they are not directly connected with them. 

 I can fully testify to the general accuracy of Kolliker's account of the 

 structure of the tonsils ; but I must add that I have been unable to 

 find ' closed follicles ' either in Man or in the Sheep ; and, on the 

 other hand, that the indifferent tissue of the so-called ' follicles ' is 

 permeated by a network of capillaries, which have exactly the same 

 relation to the indifferent tissue in which they are imbedded, as in the 

 Malpighian bodies (figs. 9, 10). So far as its structure is concerned, 

 in fact, the tonsil exactly represents a lymphatic gland, developed 



' I purposely abstain from including in this series the thyroid and pineal glands, because 

 I think it certain that the former, and probably, the latter have a different import. 



