142 REPORT— 1870. 



On the Action of some Gases and Vapours on the Red Blood-corpuscles. 

 By E. Eat Lankesteb. 



Professor Alexander ]\Iacalisteb, M.D., exhibited a sketcli of some varieties 

 of the Pronator qnadratiis. 



On a new Metliod of studying the Capillary Circulation in Mammals, By 

 Dr. S. Steicker, Professor of Experimental Pathology in Vienna, and 

 Btjrdoi^^ Sanderson, M.D., F.B.S., Professor of Practical Physiology in 

 University College, London. 



All conclusions as to the capillary circulation which are derived from obsen-a- 

 tions of cold-blooded animals are subject to the objection that their functions are 

 ■carried on under conditions considerably remote from those which exist in man. 

 It has therefore been long desirable to change the field of research to mammalia. 

 There is, however, no mammalian animal in which any external part is sufficiently 

 transparent for observation under the higher powers of the microscope. The me- 

 thod must therefore necessarily involve vivisection ; so that an anesthetic is abso- 

 lutely necessary. Most happily chloral is foimd to be completely adapted to the 

 purpose. About three grains of chloral under the skin was found to be sufficient 

 to render a fidl-sized guineapig motionless and insensible for many hom'S. 



One of us (Dr. Sanderson) was familiar with the remarkable structure of the 

 guineapig's omentum, and had already described it in connexion with another 

 inquiry. The omentum of the guineapig is a membrane of extent relatively com- 

 parable to that of man, but its structure is entirely different. First, it is attached, 

 not to the transverse colon, but to the greater curvature of the stomach ; secondly, 

 it consists, not of four layers of membrane, but two ; and lastly, it contains very 

 little fat, but in place of it a great quantity of cells, which are collected in a pecu- 

 liar way about the blood-vessels and in thek neighbourhood, partly in the form of 

 perivascular sheaths, partly in the form of little collections or nodules consisting 

 of cells lying in the meshes of a plexus of capillaries. Hence, from the simplicity 

 of its anatomical relations, and particularly from its being attached on one side 

 only to the stomach (in which respect no membrane is comparable with it), from 

 its perfect transparency, from its abundant vascularity, and from its containing 

 not only vessels, but living cells, and these cells of two kinds, namelj^, epithelial 

 and parenchymatous, it is obvious that the omentimi of the guineapig offers a 

 splendid field for observation. 



For observation the membrane must be immersed ; immersed, however, not in 

 water, for water would at once irritate and kill the tissue, but in solution of 

 common salt of proper strength. Such a solution is what physiologists call an 

 indifferent fluid, because, when it comes in contact with living cells, it does not 

 appreciably interfere with their vital processes. Secondly, it cannot be in a natural 

 condition unless it retain the temperatm-e of the living bodv. The arrangement 

 for securing this is somewhat complicated. The membrane is laid out in a glass 

 dish, whicli is supported on the stage of the microscope by a hollow brass plate, 

 through which a stream of water flows at a rate and temperature so regulated that 

 the dish and its contents are maintained at a temperature closely agreeing with 

 that of the body. 



For commencing the observation this is all that is necessary. If, however, it is 

 continued, the observer soon encoimters two difficulties, both of which must be 

 overcome. The one arises from the clouding of his objective when it is brought 

 near the warm surface of the saline solution ; the other, from the rapid evaporation 

 of the solution, and the consequent alteration of its density, and eventual desic- 

 cation of the membrane. The first difficulty is obviated by warming the objective ; 

 the second by providing for the renewal of the water contained in the bath 

 by the constant influx of fresh water at a rate corresponding to that at which 

 it wastes. 



The operative procedure is extremely simple. The guineapig having been tho- 

 roughly chloralized, is laid on a support or block, the upper surface of which is in 



