248 



REN. 



specimen shows the abrupt termination of the ci- 

 liated epithelium, e p, within the capsule, a a, 

 Some rounded particles,which are sometimes seen in 

 considerable numbers, either on the surface or in the 

 wall of the vessels c. The basement membrane of 

 the capsule, b in, beyond the termination of the 

 ciliated epithelium appears fjuite naked. Magnified 

 200 diameters. 



I am not aware that ciliary motion has been 

 detected in the kidneys of Mammalia or Birds. 

 I shall presently show that in certain fishes 

 and reptiles the cilia are not confined to the 

 situation in which they were first discovered 

 by Mr. Bowman ; but that they exist through- 

 out the greater part, if not the whole length, 

 of the uriniferous tubes. 



It appears desirable to allude here to some 

 observations which have been made since the 

 publication of Mr. Bowman's paper, and to 

 inquire how far certain statements which have 

 been opposed to his account of the Malpighian 

 bodies are worthy of consideration. It is not 

 my intention to occupy time and space, by 

 giving a history of all the contradictory opi- 

 nions which this subject has elicited. It may 

 be fairly inferred that inability to detect 

 ciliary motion within the Malpighian capsule, 

 or to verify any observation in reference to 

 which several competent authorities are agreed, 

 is the result of some defect in the microscope 

 employed, or in the eye or mind of the ob- 

 server. 



Objections have been made to two parts 

 of Mr. Bowman's description ; first, to his 

 account of the relation which the Malpighian 

 capsule bears to the basement membrane of 

 the tube and to the blood-vessels; and, 

 secondly, to his statement that the Malpighian 

 capillaries lie uncovered within the capsule. 



Bidder* made his observations on the kid- 

 ney of the male triton (Triton taeniatus). The 

 anterior part of the kidney of this animal is 

 exceedingly well adapted for the investigation 

 in question, since it is very thin and transpa- 

 rent, and is thus fitted for microscopical ex- 

 amination without further artificial preparation 

 by tearing or other means. Bidder believes 

 that the vessels do not perforate the capsule 

 to enter its cavity, as described by Mr. Bow- 

 man ; but he considers the basement membrane 

 to be introverted so as to form a covering for 

 the vessels and a complete partition of a semi- 

 lunar form between the cavity of the tube and 

 that of the Malpighian capsule. I have exa- 

 mined the kidney of the triton with great care, 

 and have satisfied myself that Mr. Bowman's 

 account of the perforation of the capsule by 

 the vessels is strictly correct, and that there 

 is no partition, but, on the contrary, a free 

 communication, between the cavity of the 

 capsule and the orifice of the tube. When 

 the vessels are distended with blood, they 

 almost fill the capsule ; on the contrary, when 

 they are empty, they shrink into a small com- 

 pass. I have examined them under both 

 conditions, and could never detect any ap- 

 pearance of a membrane reflected over them. 

 The free communication between the cavity 



* Mullet's Archiv. 1845. 



of the capsule and the orifice of the tube is 

 sufficiently shown by two phenomena which 

 I have repeatedly witnessed : first, when the 

 cilia are in action, the liquid filling that part 

 of the capsule which is unoccupied by the 

 vessels is freely propelled from the cavity of 

 the capsule into the tube; and, secondly, 

 when water is added to the specimen, loose 

 particles of epithelium from the tube are often 

 driven into the capsule, until they fill that 

 part of its cavity which is not occupied by 

 the collapsed blood-vessels. 



Dr. Gerlach* describes and figures the Mal- 

 pighian capsule as being not a blind termi- 

 nation of the uriniferous duct, but a lateral 

 diverticulum of the same structureless base- 

 ment membrane which forms the duct ; and 

 he believes that the capsule communicates 

 with the duct by means of a short neck. It 

 is not impossible that there may, in some rare 

 instances, be a diverticulum from a tube as 

 represented by Gerlach ; but as I have never 

 yet seen such a mode of connexion between 

 a tube and a capsule, and as 1 have seen 

 numberless instances of tubes terminating 

 directly in the dilatation which constitutes the 

 Malpighian capsule, I do not hesitate to de- 

 clare my decided conviction that Mr. Bow- 

 man has correctly described the structures in 

 question, -j- 



With reference to the second point above 

 alluded to, namely, to Mr. Bowman's state- 

 ment that the Malpighian capillaries lie un- 

 covered within the capsule, the observations 

 of Gerlach deserve more consideration. He 

 states that when the Malpighian capillary net- 

 work is examined after the capsule has been 

 entirely detached from it, it may be seen in 

 its whole extent covered by a thick layer of 

 nucleated cells, which are continued from the 

 inner wall of the capsule upon the Malpighian 

 vessels ; so that the latter lie introverted with- 

 in a layer of cells like the intestine wjthin the 

 peritonaeum (fig. 160.); and he supposes that 

 the secreting structure of the Malpighian bodies 

 differs from the ordinary structure of glands 



* Muller's Archiv. 1845. 



f Dr. Gerlach's opinion of the manner in which 

 the tubes are connected with the Malpighian cap- 

 sules, is founded upon appearances which he ob- 

 served after injecting the urinary tubules from the 

 pelvis of the kidney. He believes that in this man- 

 ner he succeeded in filling the Malpighian capsules 

 as well as the tubes, and that, too, as he says, after 

 he had failed in filling these parts by injection of 

 the Malpighian vessels from the artery in the man- 

 ner before described. ( Vide ante, p. 241.) On a 

 careful consideration of the drawings by which Dr. 

 Gerlach's paper is illustrated, there seems reason 

 to believe that the appearances which he describes 

 as Malpighian bodies may result from a sudden 

 bulging of the tubes produced by forcible distension 

 with the rejected material. (See Muller's Archiv., 

 1845, plate 13.) It cannot be a matter of surprise 

 that a forcible injection of the tubes from the pelvis 

 should give rise to unnatural appearances in these 

 structures ; whereas a slow infiltration of injection 

 from the ruptured Malpighian vessels, or an equally 

 slow extravasation of blood during life, while it fills 

 the capsules and the tubes, leaves these parts as 

 nearly as possible in their normal condition, and 

 affords the most satisfactory evidence as to the na- 

 ture of their connexion with each other. 



