4io 



NATURE 



\August 24, 1882 



struct the great majority of his pupils iu such a manner as to 

 enable them successfully to pass examinations, would occupy no 

 exalted position. He possessed, however, the far rarer power of 

 instilling into the minds of the best of his pupils that love of 

 original inquiry, and that deep regard for truth which are the 

 chief incentives to all scientific research of any real value. 



The investigations and Theories ok Bowman. 

 At the time when Goodsir was engaged in his investigations 

 and speculations relating to cells, Mr. Bowman was making 

 researches which were to give him a lasting place among the 

 great histologists of the century. 



His investigaiions on the structure of the kidney, 1 which was 

 published in the " Philosophical Transactions " for the year 1S42, 

 surpassed in completeness as an anatomical study, no less than 

 by the deep insight into the nature of the function discharged by 

 the organ, any investigation of like kind which had preceded it. 

 It[not only led to a more complete knowledge of the structure of 

 the kidney than was possessed of that of any other gland, but to 

 far-seeing generalisations concerning the structure of mucous 

 membranes, and of secreting organs generally, which found ex- 

 pression in a masterly article on mucous membranes, published 

 in the year 1847, in the " Cyclopaedia of Anatomy and 

 Physiology." 



Ti'ue will not permit of my giving a complete analysis of the 

 (to use a German expression) epoch-making research upon the 

 kidney ; but let me remind you that it led to a complete under- 

 standing of the relations of the Malpighian bodies to the urinary 

 tubules ; to a description which, so far as it went, was perfectly 

 accurate of the tubules themselves, though the scheme upon 

 which these tubes are arranged has, since Bowman's time, thanks 

 to the labours of Henle, Ludwig, and Schweigger-Seidel, been 

 proved to be more complicated than he had imagined, and to a 

 knowledge of the distribution of blood-vessels, not only in the 

 kidney of man and other mammalia, but also in that of certain 

 reptiles. 



His study of the structure of the tubuli uriniferi had led Mr. 

 Bowman to discover that in these, a layer of epithelial cells lies 

 upon a structureless membrane, to which he gave the name of 

 the basement membrane,- and which intervenes between the 

 epithelium and the blood capillaries, whence the materials of 

 secretion are primarily derived. His examination of the mucous 

 membranes of the body led Bowman to the conclusion that the 

 relationship so easily observed in the case of the kidney between 

 cells, basement membrane, and blood-vessels, is one which holds 

 true, not only in the case of that organ but in that of many other 

 epitheliated structures. 



" In the mucous tissue," said Mr. Bowman (Article, Mucous 

 membrane, in Todd's "Cyclopaedia,'' p. 436), "there are two 

 structures which require to be separately described, viz., the 

 basement membrane and the epithelium. The basement membrane 

 is a simple homogenous expansion, transparent, colourless, and 

 of extreme tenuity, situated on its parenchymal surface and 

 giving it shape and strength. This serves as a foundation on 

 which the epithelium rests. The epithelium is a pavement com- 

 posed of nucleated particles adhering together, and of various 

 size, form, and number. The following general observations on 

 these elementary parts will receive illustration as we advance. 

 Neither the one nor the other is peculiar to the mucous tissue in 

 the sense either of being invariably present in it, or of not being 

 found elsewhere. There are certain situations of the mucous 

 system where no basement membrane can be detected, and others 

 from which the epithelium is absent. Both, however, are never 

 absent together. Again, a structure apparently identical with 

 the bai-ement membrane is met with in numerous textures besides 

 the mucous, and all internal cavities, whether serous, synovial, 

 or va-cular, or of anomalous kind (as those of the thymus and 

 thyroid body), are lined by an epithelium." 



As a result of his anatomical studies on the kidney, Mr. 

 Bowman was led to frame a theory of renal secretion, which, 

 though opposed for a time by a master mind, has, by the pro- 

 gress of research, received complete confirmation, and which 

 was based in no small degree upon the new views of the function 

 of epithelial cells in glands. The Malpighian body, Bowman 

 showed, is the dilated commencement of a convoluted tubule, 

 and, like it, presents a delicate, structureless, basement mem- 



1 W. Bowman, "On the Structure and Use of the Malpighian Bodies of 

 the Kidney, with Observations on the Circulation through the Gland," 

 Philosophical Transactions for the year 1842, Part I., p. 57. 



' Of. cit., p. 58. 



brane. Into the Malpighian body projects a tuft of capillary 

 vessels, continuous, on the one hand, with an afferent vessel 

 derived from a branch of the renal artery, on the other, with an 

 efferent vessel of smaller size than the afferent ; both afferent and 

 efferent vessels piercing the capiule of the Malpighian body; 

 after leaving the glomeiulus, the efferent vessel breaks up into a 

 series of capillaries, which are distributed to the walls of the 

 convoluted tubes. The tuft of blood-vessels projecting into the 

 Malpighian body, Bowman described as being perfectly bare, 

 that is to say, not covered by a basement membrane, or by a 

 layer of epithelium cells. This part of his description has not 

 been confirmed by recent work, the more delicate methods of 

 modern histology allowing of a ready demo stration of a layer 

 of cells of extreme tenuity covering the glomerulus. 



The basement membrane of the convoluted tul.e was described 

 as lined by a nucleated epithelium of a finely granular opaque 

 aspect ; the neck of the tube, where it joins the Malpighian 

 capsule, and the contiguous portions of the cap.-ule were described 

 as covered by a layer of cells, differing altogether from the first, 

 being much more transparent, and possessing in certain animals 

 vibratile cilia. In some cases the whole interior of the capsule 

 h as lined by epithelium cells of great delicacy and tenuity ; in 

 others, these cells could not be traced over more than a third of 

 the capsule. Basing himself upon the altogether exceptional 

 arrangement of the blood-vessels of the glomerulus, Bowman 

 advanced the theory that this is a structure des' ined to separate 

 from the blood its watery portion. The epithelium of the con- 

 voluted tubes on the other hand, which Bowman p.iinted out to 

 be eminently allied to the best marked examples of glandular 

 epithelium," he believed to be concerned in the separation of the 

 characteristic solid matters of the renal secretion. 



I shall for the present conclude my remarks upon Mr. Bowman's 

 investigaiions and theoretical views by stating that, by his investi- 

 gations of the blood-supply to the kidney of the boa constrictor, 

 he gave the strongest proofs which could be derived from 

 anatomical evidence of the correctness of his views, and fnmished 

 great part of the knowledge required for the subsequent re- 

 searches which Nussbaum made on the secretion of the newt's 

 kidney, and which afforded the most conclusive experimental 

 evidence in favour of the theory which Bowman had advanced. 



The D scoveries of Carl Ludwig. 

 If to Johannes Miiller we must ascribe the greatest share of 

 merit as a discoverer of the general affinities, relationships, and 

 functions of glands, it appears unquestionable that to Carl 

 Ludwig belongs the credit of having, above all others, brought 

 the light of experimental physiology to bear upon the subject of 

 secretion. 



Ludwig is one of the most eminent of the physiologists who 

 have endeavoured, as far as possible, to apply the conceptions 

 derived from a study of physical and chemical processes in 

 general, to the elucidations of the functions of the organism. 

 More than anyone else has he succes-fully adapted the methods 

 of research of the chemist and of the physicist to the investigation 

 of the problems which lay before him. Above all others he is 10 

 be spoken of as the great teacher amongst all of the great 

 teachers of physiology which this century has produced. If we 

 try to find one who, from the fertility of his mind and the in- 

 fluence which he had upon men of ability, affected the progress 

 of his science in like measure to Ludwig, we revert to the name 

 of Liebig. When I say that physiology owes as much to Ludwig 

 as chemistry to Liebig, I shall, I feel sure, be doing but scant 

 justice to the great man, who at Marburg, at Vienna, and at 

 Leipzig, has won for himself the right to be called at once the 

 greatest physiologist, and the greatest teacher of physiology, of 

 his time. 



I. Ludwig s Discovery of Secreting Nerves. — It was in the 

 year 185 1 that Ludwig first announced to the scientific world 

 (Ludwig, " Neue Versuche iiber die Beihilfe der Nerven zur 

 Speichelabsonderung," Henle & Pfeifer's Zeitschrift, New Ser., 

 vol. i. (1851), p. 255) the fact that the secretion of the salivary 

 glands is under the influence of the nervous system. C. G. 

 Mitscherlich, as Ludwig points out, had surmised that the secre- 

 tion of saliva only occurs as the result of a stimulation of 

 certain nerves, i.e., the nerves of taste and the nerves supplying 

 the muscles of mastication. No attempt had, however, been 

 made, before Ludwig's, to asceriain experimentally whether the 

 stimulation of nerves supplying glands influenced directly their 

 secretion. As a subject of : tudy Ludwig chose the submaxillary 

 gland. He found that on stimulating by a succession of indue- 



