August 24, 1882] 



NATURE 



4i3 



Mipposed to be separated liy the so-called "glomeruli," whilst 

 the organic solids of tbe secreti n were supposed to be separated 

 by the epithelium lining lite convoluted tubes. 



To this theory was opposed that of Ludwig, according to 

 which the whole of the constituents watery, saline, and organic, 

 were supposed to be poured out of the vessels of the glomerulus, 

 the amount of water however being far in excess of that contained 

 in the liquids when it leaches the pelvis of the kidney. Ludwig 

 supposed thit as the secretion passed over the surface of the 

 epithelium lining tie complex tubule-, processes of diffusion 

 occurred between it, on the one hand, and the lymph bathing 

 the tissues lying outside of the basement membrane of the tubules 

 ■on the other, the direction of the current of water being from 

 without inwards. The anatomical evidence adduced by Bowman 

 was of itself well-nigh sufficient to prove the accuracy of his 

 views, which have however been placed beyond all dispute by 

 the following observations : Heindenhain introduced into the 

 Mo d a solution of sulphindigotate of sodium, u uaHy some time 

 after having divided the spinal cord in the cervical region. On 

 killing the animal some time afterwards and subjecting the 

 kiney to carelul examina:ion, it was found that the colouring 

 matter had been accumulated by the epithelium of the convoluted 

 tubules from the lymph lathing the tissues, and which contained 

 50 little colouring matter as to appear colourle s. If a sufficient 

 Time had elapsed after the injection, the colouring matter was 

 found in the form of granules or minute crystals lung on the 

 inner side of the cell in the lumen of the tubules. 



Bowman, as I have already mentioned, had in the case of the 

 boa constrictor studied in detail the blood supply to the organ, 

 which, as Jacobson had shown, differs in fishes, birds, and 

 reptiles, fiom the mode of arrangement prevailing in mammals. 



Bowman had shown that in the boa the glomeruli derived 

 id exclusively from the renal artery, and the conv. luted 

 tube cxclu ively from the common iliac vein. Nusstaum Rave 

 absolute completeness to the proof of Bowman's theory by the 

 following remarkable experiment. Experimenting on the newt, 

 in which the bli od-supply of the kidney is similar to that of the 

 h .a, he found that, when he tied th; renal artery, he arrested 

 almost entirely the secretion of water in the kidney, but that the 

 excretion of urea a' d other solid matters, and amongst others of 

 the colour ng matter already used by Heidenhain, viz., indigo 

 carmine, continued. Ligature of the renal branches of the com- 

 mon iliac vein stopped the secretion of organic solids without 

 impeding that of water. 



The most recent Theories advanced in Explanation of 

 the Phenomena of Glandular Secretion. 



Having brought before you the most salient facts with which 

 we are acquainted, which appear to throw the most light upon 

 the general physiology of glandular secretion, I wish, before 

 concluding, to speak of the theoretical views which have been 

 advanced in explanation of a large number of the facts. 



In the first place, I have to confess that our ignorance is 

 absolute as to the cause of the specific endowment of d.fferent 

 secreting cells, in virtue of which they produce new bodies at 

 the expense of certain of the materials supplied to them by the 

 lymph, or separate particular constituents from the lymph, to tbe 

 exclu-ion of others which are equally abundant in the liquid. 

 We express the full measure of our ignorance when we state 

 'hat the difference in function of different gland cells is due to 

 differences in endowment of the protoplasm of the cell, which in 

 no case is explained by any objective characters of the cell. 



The phenomena of the secretion of water, which forms so 

 large a part of every secretion, have given rise, however, to 

 numerous speculations, concerning which I may make a few 

 remarks. 



The primitive view that the glands are organs in which is 

 strained off from the blood water holding certain substances in 

 solution has, in a modified manner, found favour with some even 

 to our own days, and appears indeed, at first -ight, to be borne 

 out by certain facts. Thus within wide limits the amount of 

 water secreted by the kidney depends upon the pressure of blood 

 in the glomeruli. Any circumstances which will lead to an in- 

 crease of pressure in these vessel- (as increase of blood pressure 

 generally, division of renal nerves, division of the splanchnics, 

 especially when combined with stimulation of the spinal cord), 

 by dilating the branches of the renal artery, will lead to this 

 result. At first this would seem to show that the process of 

 separation of water, in the kidney at least, is but a process of 

 filtration, though a remembrance of the famous experiment of 



Ludwig, referred to at an earlier period, on the relation between 

 the pressure of secretion of saliva and that of the blood in the 

 arteries, would impose caution in drawing the conclusion. What 

 are the facts, then, relating to the blood pressure in vessels 

 in other organs of the body, and the transudation of liquid from 

 them ? 



If an increased arterial pressure led ipso facto to an increased 

 transudation through the capil ary walls, it would follow 

 that the amount of lymph and the pressure of the lymph- 

 stream would ri-e with the rise of the arterial pressure, but 

 direct experiments on this matter have led to an opposite con- 

 clusion. The experiments of Paschutin and Eniminghau--, carried 

 out under Ludwig's direction, have shown that when the arterial 

 pressure in the extremities is increased, there is no corresponding 

 increase in the lymph produced. Again, when the chorda tympani 

 is stimulated in an animal into whose blood atropia has been in- 

 troduced, the vascular dilatation which is produced, and which 

 is produced, and which is then unaccompanied by secretion, does 

 not lead to an increased production of lymph, which would 

 make itself evident by the gland becoming (edematous. How 

 then are we to account for the How of water through a gland? 

 By ascribing it to an influence which is exerted by the gland 

 cell, in the first place, upon the liquid which environs it, viz. the 

 lymph. And accordingly, even in the case of the glomeruli of 

 the kidney, we conclude that the water is separated as a di-cct 

 result of the activity of the layer of transparent epithelium cells 

 which cover them. Hering has advanced a strictly physical 

 theory, which would account for the mode in which certain cells 

 exert this influence, by supposing that there is produced within 

 them bodies which, like mucin, have a great affinity for water 

 and which then pas into the secretion ; and which therefore lead 

 to a current of water passing through the cell ; but the theory is 

 one which cannot be admitted, because, as Heindenhain points 

 out, the passage of water through a gland occurs in cases w here 

 there is no constituent in the cells, at all resembling mucin in its 

 affinities or behaviour towards water. 



I feel inclined io say that the speculations, necessarily indefinite 

 though they are, of Professor Heindenhain afford the best 

 explanation of the phenomena, Heindenhain starts from tbe 

 fundamental fact that during secretion only as much water 

 passes out of the blood-vessels of the gland as appears in its 

 secretion, seeing that, however long the process of secretion 

 may continue, the gland never becomes cedematous, nor does the 

 current of lymph from it increase. 



The volume of liquid filtered through the blood capillaries 

 adjusts itself exactly to the volume of liquid separated by the 

 cells. This equality in the amount of liquid secreted and 

 filtered appears only explicable on the supposition that the act 

 of secretion is the cause of the current of water — in other words, 

 that the water which the cells lose in the formation of the 

 secretion generates changed in them which can only be com- 

 pensated for by an abstraction of water from the immediate 

 environment. 



Within certain limits, Heindenhain continues, we may form 

 purely physical conceptions of the process. We may conceive, 

 lor instance, the whole protoplasm of the cell to have a certain 

 affinity for water. The cells at their contact with the basement 

 membrane may be supposed to be able to abstract water from it ; 

 the loss which the membrane sustains will be made up by the 

 lymph, and this again will influence the blood in the capillaries. 



The passage of water into the cells w ill go on until a period of 

 equilibrium is attained ; but at that time the current of water 

 from the capillaries through the lymph to the cells will cease. 

 We may conceive further, reasons Heidenhain, that the pas-age 

 of water out of the cell is hindered by such obstacles to the pro- 

 cess of filtration as are represented by resistance opposed to it 

 by the superficial border layer of protoplasm. If we now conceive 

 that, for example as a result of nerve stimulation, the gland cells 

 pour out water, the condition of equilibrium which existed 

 between cell, basement membrane, lymph, and capillary will be 

 disturbed, and a current of liquid set in from the last to the 

 first, and continue as long as the activity of the cells continues. 



It is not difficult moreover, Heidenhain remarks, to form 

 physical conceptions of the processes whereby water may be 

 separated from the cell itself. It is conceivable, for instance, 

 that the protoplasm of the cell may contract after the manner 

 which occurs in many infusoria, and which in them leads to the 

 accumulation of water in droplets, forming vacuoles, except that 

 in the case of the secreting cells the water is poured out on the 

 outside and not on the inside of the cells. Or, again, it is possi- 



