44 



NATURE 



[June 28, 1917 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous cominunications.] 



Chinese and Persian Giraffe Paintings. 



In Nature of February 18 and July 29, 1915, and 

 in the American Museum Journal for last year, figures 

 were published of ancient Egyptian and also of late 

 fifteenth-century representations of the giraffe. To 

 this series of olden-time drawings may now be added 

 one from Chinese sources, dating probably from the 

 early Ming period, a reproduction of which is show:n 

 in the accompanying illustration. 



The original is a large unsigned painting in dull 

 colours on silk, executed with considerable firmness 

 of style and finish, the trappings and figures of, the 

 attendants receiving especial attention. The general 



1^ 



Early Chinese picture of a giraffe. 



Style of the painting and the state of preservation of 

 the fabric and colouring would seem to indicate an 

 antiquity of at least three or four hundred years. In 

 the opinion of the owner, Mr. A. W. Bahr, a dealer 

 in Chinese works of art in New York, the painting is 

 still older. 



Through the kindness of Miss Greene, in charge of 

 the private library of Mr. J. P. Morgan in this city, 

 the writer has had the privilege of examining a num- 

 ber of old manuscripts containing animal paintings, 

 among them being one which is probably the earliest 

 known English bestiary. Another is an extremely in- 

 teresting Persian bestiary of the thirteenth century, 

 which has been briefly noticed by M. Claude Anet in 

 the Burlington Magazine for 1913 (vol. xxiii.. No. 24). 



Among the admirably drawn coloured figures of this 

 Persian MS. is one of the giraffe, which is strikingly 

 like the Chinese painting already referred to. It 

 might almost be said that one has served as a model 

 or general design for the other, and undoubtedly the 

 Persian is the more ancient. The inference appears 

 warranted, therefore, that pictures of the giraffe and 



NO. 2487, VOL. qql 



other Western animals were introduced into Persia, 

 through trade routes so early as the thirteenth century,, 

 and thence found their way into China, where they 

 were copied by native artists. C. R. Eastman. 



American Museum of Natural History, New York. 



The Nature of Renal Activity. 



May I be permitted to explain what seems to me 

 to be a misunderstanding of Prof. Cushny's position 

 contained in the review of his monograph in Nature. 

 of June 14? 



No physiologist at the present time can hold that 

 the kidnev is a " mere machine," if by that it is meant 

 that such simple physical and chemical forces as those 

 of diffusion and osmosis are sufficient to give a com- 

 plete solution of its activity. The fact that the fluid 

 vvhich leaves the kidney Vias a much higher osmotic 

 pressure than that of the blood from which the fluid 

 was forrned shows at once that work has been done 

 by the cells of the organ. In our present ignorance 

 we say that this is by means of the "vital" activities 

 of the protoplasmic mechanism, which transforms 

 chemical energy derived from oxidation of food mate- 

 rial into osmotic energy. In using the word "vital," 

 most of us have no intention of begging the questioa 

 as to whether or not these activities involve more than 

 forces present in the non-living world, acting in a 

 special complex system, however much we may feel 

 that further investigations will show that there is no 

 necessity for the assumption of a form of energy pecu- 

 liar to living beings. 



Where Prof. Cushny's position, as I understand it, 

 is an advance lies in the simplification which it intro- 

 duces into many aspects of the problem. To py,t it 

 very briefly, it is this : — In the glomerulus, fluid is 

 filtered from the blood by means of the. arterial pres- 

 sure. This fluid consists of all the constituents of 

 the blood minus the colloids, the latter, of course, 

 including the blood corpuscles. It contains ajl that the 

 final urine contains, but^in very dilute solution. So far,, 

 this is the view put forward by Prof. Starling, but the 

 further development diverges from that given by Prof. 

 Starling. There are two possible ways in which this 

 dilute glomerular filtrate might be made more concen- 

 trated — one by removal of water, the other by the 

 addition of solutes contributed by the secretory activity 

 of the cells of the tubules. 



Now Prof. Cushny, after a careful examination of 

 the evidence that has been brought forward in support 

 of the second view, comes to the conclusion that none 

 of this withstands criticism, so that the first method 

 must be the one accepted. But, while previous theories 

 regarded reabsorption of water and that of certain 

 of the solutes as separate processes, the new point of 

 view is that the fluid reabsorbed has the composition 

 and concentration of the diffusible substances con- 

 tained in the blood, with the omission of certain excre- 

 tory products, such as urea. As Prof. Cushny puts it, 

 "Locke's fluid" is reabsorbed. Naturally, some 

 reason has yet to be found why urea fails to^ be 

 absorbed, while sodium chloride, glucose, and amino- 

 acids are, but the whole of the phenomena met with 

 can be satisfactorilv explained on this "modern view.' 

 For example, sulphates are foreign to the blood, ana 

 are not reabsorbed. Whatever is present in blood in 

 true solution is present in the glomerular filtrate, but 

 only the constituents of Locke's fluid (plus amino- 

 acids) are reabsorbed and in the concentration present 

 in that solution. Doubtless we shall be able in the 

 future to say why the cells behave in this^ way. The 

 process may be called " selective discrimination," if 

 any comfort is obtained from doing so, but so maV 

 the behaviour of parchment paper towards gelatin and 



