144 SPECIAL HISTOLOGY. 



retrograding blood corpuscles as will be described to occur 

 in the pulp, in the following section. 1 



1 [The Malpighian follicles of the spleen present three points of importance to 

 the investigator. 1. Whether they have a capsule and what is its nature? 2. The 

 arrangement of their vessels. 3. The structure of the substance which they contain. 



1. The capsule and its nature. — We have been quite unable to convince ourselves 

 of the existence of any such capsule as that described by Professor Kblliker, in the 

 Malpighian. follicles of Man, the Sheep, the Pig, the Cat (Kitten), or the Rat ; in all 

 of which we have made very careful investigations with regard to this point. In 

 Man, in the Pig and in the Cat, we were unable to distinguish any boundary at all 

 between the follicles and the surrounding red pulp — the substance of the one ap- 

 pearing to pass into the other. At the line of transition, however, the indifferent 

 tissue of the follicle underwent a partial metamorphosis and broke up, wben teased 

 out, into spindle-shaped bodies, containing " nuclei," or short delicate fibres with 

 " nuclei," exactly resembling, in Man, the structures described by Professor Kblliker 

 as peculiar fibres and represented in fig. 227. 



In the Rat this border zone of metamorphosed tissue was somewhat broader and 

 firmer and when the follicle was compressed, appeared, particularly under a low 

 power, like an indistinctly fibrous coat such as Professor Kblliker describes ; but 

 when closely examined, it was readily seen to be no distinct closed capsule, but to 

 pass gradually, on the one hand, into the pulp and on the other, into the contents 

 of the follicle. The same is true of the Malpighian follicles of the Sheep, where the 

 appearance of a capsule, under a low power, is often very distinct ; and where im- 

 perfect elastic fibres may be met with in it. 



In fact, our own observations are perfectly in agreement with those of Mr. 

 Wharton Jones (British and Foreign Med. Review, Jan., 1853), and have led us 

 completely to the opinion of Remak (Ueber runde Blut-gerinnsel und iiber Pigment 

 Kugelhaltige Zellen, Midler's 'Archiv,' 1852), that the capsules of the follicles are 

 by no means their essential element, and that we must consider the spleen to be 

 formed by two principal constituents ; the first being the parenchyma — and the 

 second, a superadded fabric of blood-vessels, nerves, lymphatics, elastic and con- 

 tractile elements. The manner in which the latter are arranged in and about the 

 parenchyma is, in a manner, accidental, and very variable. It may be, as Remak 

 says, either inter capillary, as in the pulp; or vaginal, as in the sheaths of the 

 arteries ; or encysted, as at the angles of division of the arteries, in the Malpighian 

 follicles of the Sheep. 



To insist, therefore, upon the follicular arrangement of the spleen, or indeed of 

 any other of the vascular glands, as Sanders (On the Structure of the Spleen, 

 'Annals of Anatomy and Physiology,' 1850) and Kblliker do, seems to us to mistake 

 accidental for essential characters. 



The results of comparative anatomical examination are strikingly in favour of this 

 view of the matter. 



The Malpighian follicles of Birds and Amphibia have no capsules (Remak, Leydig). 

 In Bombinator igneus, according to Leydig, a white substance, the representative of 

 the Malpighian follicles, lies in the middle of the spleen, surrounded by a red cortical 

 pulp, into which it directly passes. 



On the other hand, Coluber natrix, a Reptile, presents the very opposite characters. 



