TRANSACTIONS OF SECTION D. 783 



13. On the Diatomaceovs remains in the Lake Deposits of Nova. Scotia. 



By A. H. Mackat. 



Subsection of Physiology. 



1. On the Demonstration of an Apparatus for Recording Changes of Volume. 

 By Professor E. A. Schafer, F.R.S. 



Remarks on the Problem of Aquatic Breathing. 

 By Professor McKendrick, M.D., F.li.S. 



3. On the Biliary Concretions ; demonstrating a Uniformity in the Construc- 

 tion of Concretions in the Animal, Vegetable, and Mineral Kingdoms. 

 By Dr. G. Harley, F.R.S. 



4. On the Secretion of Oxalic Acid in the Dog. 

 By T. Wesley Mills, M.A., M.D. 



This paper describes the results of a diet of (1) Flesh, (2) Flesh and fat, and 

 (3) of Flesh and carbohydrates, on the secretion of oxalic acid in the dog. It 

 consists of (1) A comparative examination of the different methods in vogue for 

 the quantitative determination of oxalic acid in the urine of man, and shows that 

 Schultzen's method is the best ; (2) The perfecting of a method for the determi- 

 nation of oxalic acid in dog's urine; (3) An application of this method to the 

 problem proposed in the heading of this paper. 



A dog was kept under constant observation, punctually fed daily, the urine 

 removed, its quantity, reaction, specific gravity, &c, determined, diluted to a 

 definite volume, filtered, and its nitrogen and oxalic acid determined. A 

 complete tabular statement of the results was given. The principal conclusions are 

 as follows : — 



(1.) Under all three diets given oxalic acid was daily found in the urine in 

 determinable quantity. 



(2.) The average for seven days' flesh diet was "0113 gramme. It will be seen 

 that this was larger than by either of the other diets, and the strong acid reaction 

 of the urine throughout points to the flesh diet as a cause of the same. 



(3.) The average under diet (2) for five days, *0055 gramme, denotes a decided 

 falling off under the substitution of fat for flesh. 



(4.) The average under diet (3) for seven days is "0033 gramme, and shows that j 

 carbohydrates do not increase the secretion of oxalic acid, but the contrary. 



The animal was throughout kept in nitrogenous equilibrium. 



5. On the Mechanism of Absorption. By Professor E. A. Schafer, F.R.S. 



It has hitherto been almost universally held that the mechanism of absorption 

 of alimentary substances from the intestinal tract is strictly analogous to the 

 passage of fluids through moist animal membranes, and it has been considered a 

 sufficient explanation of the process to assert this belief, and thus to account for 

 the passage of the comparatively diffusible peptones, sugars, salts, and water, into 

 tie albuminous fluids which occupy the blood-vessels and lymphatics. 



But there are many objections to regarding absorption as a mere example of 

 physical osmosis. For the difference in the osmotic equivalents of the digested 

 food materials and of the blood or lymph is comparatively small, and quite in- 

 sv.i'ricient to account for the rapidity with which absorption may occur. Moreover, 



