524 TRANSACTIONS OF SECTION I. 



Section I.— PHYSIOLOGY. 

 President oe the Section. — Professor J. S. Macdonald, B.A. 



THURSDAY, AUGUST 31. 



The President delivered the following Address : — 



The special difficulties of physiology are well known to a large section of my 

 audience, but it may be permissible to illustrate them by reference to an indi- 

 vidual case. Take for example those small capsules which are found in the kid- 

 neys at the very summit, so to speak, of the problem of renal secretion. These 

 small bodies each occupy a space of less than two thousandths of a cubic milli- 

 metre. Within their interior they contain several different kinds of blood-vessels 

 that represent the structures of greatest mechanical interest when dealing with 

 the circulatory system, omitting of course the heart. This almost complete 

 sample of the circulatory mechanism, itself formed of a congeries of parts and 

 unitary mechanisms, is enclosed by two or three thousand cells of specific 

 glandular function. Every one of these cells again is a complex of mechanisms 

 about which we cannot rightly think until we reduce our conceptions to the level 

 of molecular dimensions. Enclosed then in this minute space, within a mass 

 that weighs two thousandths of a milligramme, lie quite a series of the problems 

 in which physiology is interested. 



The difficulties occasioned by this minuteness of parts, and by the manner 

 in which they are complexly mixed together, render direct investigation of single 

 problems possible only in the very simplest cases, as, for instance, the red blood 

 corpuscle and the nerve-fibre. 



A consideration of the dynamic properties of the red blood corpuscle is per- 

 haps the simplest task in physiology. By the -aid of the centrifuge these bodies 

 can be obtained free from the embarrassing presence of other cells, may even 

 be washed and immersed in definite solutions of known value. In addition, 

 these compressed discs, the study of the forces normally compressing them open 

 to research by variations in the quality of the surrounding solutions, contain no 

 nuclear reactions and but the one material of primary dynamic importance. 



Everyone knows, however, that even in this case the dynamic conditions are 

 being investigated largely in an indirect fashion. The material of primary im- 

 portance, haemoglobin, is stable except with regard to the one well-defined re- 

 action with oxygen to which it owes its utility. This material may readily be 

 obtained pure and its properties examined in homogeneous solutions, and these 

 properties may again be studied after adding to this solution such secondary 

 substances, lipoids and inorganic salts, as are also present in the red blood cor- 

 puscle. In the hands of members of this Section such studies are not only 

 increasing our knowledge of the properties of haemoglobin, but are also rapidly 

 leading to a knowledge of those very dynamic conditions with which it is 

 surrounded when present within its microscopical site in the red blood cor- 

 puscle. In this very simple instance, the parts of the mechanism being known, 

 it is possible to arrange them in such a fashion as to limit our conceptions of 

 the way in which they are actually arranged within the body. 



