GLANDS. 435 



My view of the nature of the Malpighian body differs, in 

 some respects, from that entertained by Mr. Bowman. The 

 proper Malpighian capsule is invariably lined by innumerable 

 granular cells ; for this single and simple reason, therefore, I 

 regard this body as a secreting organ as much as the urini- 

 ferous tubes themselves, which present an organisation essen- 

 tially the same. I differ, therefore, from Mr. Bowman, who 

 considers the epithelium of the tubes as the sole true secreting 

 agents of the urine. I conceive that this fluid is formed in 

 every part of the tubular and- Malpighian surface of the 

 kidney, and I dissent from the opinion that the Malpighian 

 body is an apparatus destined for the simple separation of the. 

 watery parts of the urine apart from any act of secretion. 



Nevertheless, I so far agree with Mr. Bowman in his 

 theory, as to consider that the greater portion of the more 

 watery parts of the urine proceed from the Malpighian bodies ; 

 not, however, by an act of simple separation, but by one of se- 

 cretion. The peculiar arrangement of the blood-vessels, and 

 the presence of ciliated epithelium at the entrance to the 

 tubes, are facts in themselves sufficiently conclusive of the 

 accuracy of this view : as, on the other hand, I conceive the 

 great extent of secreting surface presented by the tubes to 

 be in itself sufficient to prove that at least a portion of the 

 aqueous constituent of the urine emanates from this surface. 



An accurate knowledge of the pathology of the kidney 

 and urine would, doubtless, furnish arguments conclusive as 

 to the relative functions and importance of the tubes, and 

 their enveloping plexus and the Malpighian bodies. 



The reader will at once observe that one of the arguments 

 in favour of Mr. Bowman's theory, urged in the preceding 

 exposition, does not hold good, in consequence of its want of 

 accordance with the true structure. I allude to the supposed 

 entrance of the plexus into the cavity of the proper Malpighian 

 capsule. 



In birds and reptiles, the Malpighian plexus is not formed 

 of a number of convoluted vessels, resulting from the repeated 

 subdivision of the afferent artery, as is the case in all the 

 Mammalia, but simply consists of a single coiled vessel, so 



