iv INTRODUCTION 



indicate relative position with regard to head and tail, while 

 dorsal and ventral are used for the anterior and posterior of 

 human anatomy. Medial is used to imply proximity to the 

 middle line, lateral being the contrasting term. Proximal refers 

 to that part of an organ or structure nearest to its centre or to 

 its attachment to the body, distal being the opposite adjective. 

 In speaking of muscles the fixed point of attachment is the 

 origin, the attachment on the part to be moved is its insertion. 

 INJECTING. In many cases it is almost impossible for the 

 beginner to trace the blood-vessels unless they are filled with some 

 colored substance which renders them more easily seen. This 

 is especially true of the smaller vessels. Injection is also frequently 

 convenient in tracing other vessels like those of the urogenital 

 system. 



Various substances ('injection masses') have been devised for 

 filling the vessels. The essential features of a mass are that it 

 have color, that it flow freely when injected, and that it soon harden 

 so that it will not escape from a vessel accidentally cut. Within 

 recent years a starch mass has been largely used, and as this answers 

 all the purposes of these guides it is described here : 



Corn-starch 400 pts. by volume 



2% chloral hydrate in water 400 " 



95% alcohol 100 " 



Color and glycerin (equal parts) . . 100 ' ' 

 The mixture should be thoroughly mixed by stirring and 

 strained through cheese-cloth or paper cambric, stirring during 

 the operation. The starch and color quickly settle, hence the 

 mixture has to be stirred while using. It will keep indefinitely, 

 but of course must be thoroughly mixed each time before using. 



The colors commonly used are vermillion,* insoluble Prussian 

 blue, chrome green, and chrome yellow. The vermillion is usually 

 used for the arterial, the blue for the venous system, but it is 

 often advantageous to use chrome yellow instead of blue, as it 

 contrasts better with dark organs like the liver and kidneys, while, 

 when a blood-vessel occasionally bursts in injection, the viscera 

 are not so badly stained. 



* Care should be taken to get true vermillion (mercuric sulphide), as much 

 that masquerades under that name is red lead colored with cosine. This 

 works disadvantageously as the cosine dissolves in the liquids in which the 

 specimens are preserved and stains everything indiscriminately. 



