236 



indication of the existence of genuine muscle amongst the 

 radiating tissue of the human iris, no such necessity can 

 present itself in the eye of the pig, in which the sphincter 

 pupillee is antagonised by no less than five distinct sets of 

 muscular fibres, leading to the inference that a well-con- 

 ducted series of experiments upon the eye of that animal 

 would develop important results. 



On the BEST Methods 0/ Studying Transparent Vascular 

 Tissues in Living Animals. By Eichard Caton, M.B., 

 Assistant Physician to the Liverpool Infirmary for 

 Children. 



During the last three years, the researches of Professor 

 Cohnheim and other German observers have rendered the study 

 of the relation between vessels and parenchyma particularly 

 interesting to physiologists. 



The amoeboid movements of white blood cells ; their relation 

 to pus corpuscles ; their spontaneous division, according to 

 Klein ; the entrance of pigment cells into the vessels, as 

 recently described by Saviotti ; along with other points, are 

 just now deserving careful study by microscopic observers. 

 The following enumeration of the chief transparent tissues 

 suited for purposes of study in vertebrate animals, along with 

 a description ot some improved methods of examination, may 

 perhaps be useful to those who study the circulation from a 

 physiological point of view; and also to those who are interested 

 in it merely as a microscopic object. 



I. Circulation in Animals breathing by Lungs. 



1. The Frog. — In studying the circulation in any animal, 

 the first essential is, that it be kept still on the stage of the 

 microscope. This has generally been attempted by mechanical 

 restraint, or sometimes by the use of chloroform. 



I have found the subcutaneous injection of the hydrate of 

 chloral answer much better. A solution of four grains to the 

 drachm is a convenient strength, and the rule for its use for the 

 frog is very sim])le : as many minims should be injected as the 

 frog is drachms in weight. The injection is made under the skin 

 of the back, with a morphia syringe. In the case of a 

 painful operation a larger dose is needed, or woorali may be 

 employed. 



A grain of woorali in powder is added to an ounce of water ; 

 it dissolves to a slight extent. Two or three minims of this 

 solution (previously shaken) injected, will render a frog of six 



