694 



PHYSIOLOGY. 



ciency of the fluid available, will be retained. 

 Thus uric acid requires some eight thousand 

 times its bulk of water at the temperature of 

 the blood to hold it in solution ; and if it 

 be not dissolved it speedily crystallizes, with 

 disastrous consequences in the shape of dis- 

 ease. Not less than three and a half pints 

 of fluid should be consumed by any person 

 every twenty -four hours, and, when the body 

 is bulky, four or even five pints should be the 

 average. The fluid should be chiefly either 

 pure water or water in which the simplest 

 extracts are held in solution. Fluid heavily 

 charged with solid matter can not fairly be ex- 

 pected so entirely to rid itself of this burden in 

 the process of digestion and absorption as to 

 be available for solvent purposes generally. An- 

 other urgent reason for drinking freely of bland 

 fluids is to be found in the need of diluents 

 something slightly different from mere solu- 

 tion. Many of the solids of the tissue waste 

 are of a nature to irritate and even disorganize 

 the kidney if they be brought to that organ for 

 excretion in too concentrated a form. There 

 is no reason to suppose that the kidneys ere 

 liable to suffer from overwork if the specific 

 excreting power of their cells be not too heavi- 

 ly taxed. If only the products of disassimilation 

 be diluted, so that they can be passed through 

 the kidney by the simple process of exosmosis, 

 the organ will discharge its function without 

 injury or exhaustion. As a matter of fact and 

 experience, those who drink innocuous and 

 unstimulating fluids freely do not suffer from 

 kidney trouble. 



The fact that the woody fiber which is con- 

 sumed in large amounts by herbivorous ani- 

 mals is digested to a considerable extent, long 

 suspected, has been experimentally proved by 

 the researches of Hofmeister and Tappeiner. 

 Hofmeister showed that digestion of cellulose 

 took place in the rumen of the sheep; also 

 that the fluid from the rumen of a freshly killed 

 sheep and the mixed saliva had this power. 

 Experiments with the fluids of other animals 

 resulted differently. Tappeiner's experiments 

 indicated that the digestion is effected by a 

 fermentative process, with the evolution, in 

 certain cases, of carbonic acid and marsh gas, 

 and in other cases of carbonic acid and hydro- 

 gen. From these experiments, and from exami- 

 nations of the breath of sheep, it is estimated 

 that the digested cellulose sets free in the body 

 of the animal 96 per cent, of the energy that 

 the same weight of starch would do. 



R. H. Chittenden and George W. Cummins 

 have published accounts of experiments they 

 have made, by artificial digestion, upon the 

 relative digestibility of fish-flesh in gastric 

 juice. They used for gastric juice a solution 

 of five grammes of pepsin in one litre of dilute 

 hydrochloric acid. In this they placed, in two 

 portions for each experiment, weighed and 

 equal portions of carefully prepared fish-flesh 

 which had been cooked, and exposed it to a 

 temperature of from 38 to 40 C. for twenty- 



two hours, with occasional stirring. The re- 

 sults of the 'experiments, which the authors 

 have represented in elaborately detailed ta- 

 bles, show that the average digestibility of 

 fish-flesh is far below that of beef similarly 

 cooked. In but two instances, in the cases of 

 shad and of lake white-fish, does the digesti- 

 bility of fish-flesh approach that of beef, though, 

 from the average of the experiments, several 

 fish are as easily digestible as mutton, lamb, 

 and chicken. Fish with white flesh appear to 

 be more easy of digestion than those with more 

 or less red flesh. The difference between the 

 digestibility of the light and dark meat of the 

 same fish is somewhat striking. A similar 

 difference, though very much smaller, is to be 

 noticed between the light and dark flesh of the 

 chicken. This difference in digestibility is in 

 part due, without doubt, to the amount of fat 

 present, but not always, for the flesh of fresh 

 cod contains but little fat, yet it was one of the 

 most indigestible of the white fish experiment- 

 ed with. These results agree, generally, with 

 those obtained by Pavy from similar experi- 

 ments. 



The Glandular System. In a discussion in the 

 Physiological Society of Berlin on the functions 

 of the sebaceous glands, Prof. Fritsch contro- 

 verted the hypothesis of Herr Una and others, 

 that these glands served only to lubricate the 

 hairs, while the globiform glands, commonly 

 called the sudoriparous glands, lubricate the 

 skin and induce the formation of subcutaneous 

 fat, and that the perspiration is discharged into 

 the sweat-pores, or, rather, into the extreme 

 ends of the straight canals into which the sweat 

 finds its way out from intercellular spaces 

 through the stomata. He was sustained, in 

 general, by Prof. Du Bois-Reymond, Prof. Wal- 

 deyer, Dr. Gad, and Dr. Lassar, who maintained 

 that all known observations and experiments 

 were to the contrary of this hypothesis, and in 

 favor of the view that the sebaceous glands 

 provide fat for the skin, while the globiform 

 glands have the production of sweat assigned 

 to them. 



It has been ascertained by the labors of Lud- 

 wig, Heidenhain, and Nussbaum, that the kid- 

 ney-tubules, where lined by cells containing 

 protoplasm, are differentiated in their function 

 from the thin-walled Malpighian capsules at 

 the extremities of the tubules ; and it is gener- 

 ally accepted that the capsule serves simply as 

 a diffusion and filtration membrane through 

 which pass water and inorganic salts, which 

 make up the bulk of the urine, while the large- 

 bodied cells of the tubules, particularly of ti 

 convoluted portions, may be looked on as true 

 secretory mechanisms, which have the power 

 of actively selecting substances, as urea and 

 urates, from the lymph, and probably also o1 

 manufacturing specific products. Dr. Drese 

 has extended the evidences for the differentia 

 tion of function between these two parts of I 

 secretory mechanism of the kidney, from the 

 results of his experiments on frogs, which indi- 



