THE SPLEEN. 145 



§168. 



The red substance of the spleen, the pulp, or parenchyma of 

 the spleen, is a soft reddish substance, which fills up all the in- 



Here the red pulp is absent and the spleen has, as nearly as possible, the structure 

 of an ordinary lymphatic gland, consisting of a fibrous stroma, containing cavities 

 full of indifferent tissue, through which a capillary network, arising from the vessels 

 of the stroma, is distributed (Leydig, ' Anatomisch-Histologische Untersuchungen 

 iiber Fische und Reptilien/ 1853). 



In Fishes tbe same variation occurs. In Hexanchus there are thick-walled Mai- 

 pigbian corpuscles (Leydig). In other PJagiostomes and many osseous Fish there 

 are no distinct follicles, but the indifferent follicular tissue follows the sheaths of the 

 arteries. 



2. The arrangement of the vessels of the Malpighian follicles. — Johannes Miiller, 

 who gave the first good account of the Malpighian follicles of vegetable feeders 

 (Midler's 'Archiv,' 1834), not only states that the follicles are, what all recent re- 

 searches have shown them to be — the representatives of portions of the sheaths of 

 the arteries, but also that the arterial twigs which supply them " sometimes run be- 

 side the Malpighian bodies without giving any branches to them, sometimes pass 

 straight through the corpuscles" (p. 88). However, he appears to be inclined to 

 the opinion that the arterial twigs pass " not so much through the middle of the 

 corpuscles" as in the thickness of their walls. 



All subsequent writers have affirmed that the arterial twigs pass over the surface 

 and not through the substance of the Malpighian follicles, with the exception of 

 Giinsburg and of Dr. Sanders — who states, not in the paper we have cited, but in a 

 subsequent communication to the Edinburgh Physiological Society (Jan. 31st, 1851), 

 that by a peculiar method of preparation, he had observed arterial twigs passing dia- 

 metrically through the substance of the follicles, " stains of blood also, often in linear 

 arrangement, indicating capillaries, were seen in the interior of the sacculi." With 

 regard to the latter point, it will be observed that, in the text, Professor Kblliker 

 also records a single observation of minute blood-vessels in the Malpighian follicles 

 of the Cat. 



In all the Mammalian spleens we have examined (Man, Sheep, Pig, Cat, Rat), we 

 have observed the passage of arteries through the Malpighian follicles and the 

 existence of a capillary network in them, with the utmost ease ; we are, indeed, at a 

 loss to comprehend how it is that previous observers have so generally overlooked 

 facts so patent. The method we have pursued has been merely to make a tolerably 

 fine section, containing a Malpighian follicle, with a sharp knife — to spread it out 

 with needles, adding nothing but a little weak syrup and then, placing a thin glass 

 plate over it, we have examined it with both the simple and the compound micro- 

 scope. The use of the former is especially to be recommended, because by manipu- 

 lating the covering plate, the whole follicle may be readily rolled about under the 

 eye, and the clearest evidence thus obtained that the arterioles pass through and not 

 over the surface of, the follicles. Acetic acid should not be used, as it renders the 

 contents of the follicle opaque ; but the syrup is of great service, as it keeps the 

 coloring matter of the blood in the capillaries and renders them extremely obvious. 



ii. 10 



