The Vascularization of the Hnman Testis. 465 



solution is forced into the artery under a pressure of 60-80 mg. 

 of mercury, and is allowed to pass through the vascular tree and 

 issue from the returning veins. After a short interval, depending 

 upon the size of the organ, the fluid pouring from the vein will 

 contain little blood and later will be clear. The gland, however, 

 has become firm from the passage of fluid from between the endo- 

 thelial cells of the capillaries. It seems odd that a pressure below 

 the normal systolic blood pressure should cause this extravasation, 

 but this may perhaps be due to the rapid death of the endothelial 

 cells. Air is then forced into the artery and in an incredibly short 

 time bubbles of air are seen at the openings of the veins, the organ 

 becomes soft and no sign of tension is manifest in the vessels, which 

 are now thoroughly emptied. Then follows a similar injection of 

 equal parts of absolute alcohol and ether, and after the appearance 

 of this mixture at the openings of the veins a second "blowing 

 out" is resorted to. In this instance, however, the cells lining the 

 vessel walls are more or less fixed with absolute alcohol and ether 

 and their lumen is open and ready for the celloidin injection mass. 



The celloidin, usually 7 per cent., colored with vermillion or 

 finely powdered lamp black, readily enters the vessels against no 

 backward pressure and flows into and completely fills the smallest 

 vessels. 



By using a thin celloidin for the arterial and capillary vessels, 

 and a thicker celloidin for the veins, a very instructive and beau- 

 tiful double injection is obtained with comparative ease. Such 

 specimens are valuable for microscopic work, for clearing in 1 per 

 cent, potassium hydroxide and glycerine and for corrosion work. 

 The vermillion and lamp black withstand the ordinary laboratory 

 reagents even in concentrated forms. The method of corrosion used 

 is simply that of peptic digestion as devised for such studies by 

 Dr. Mall.* In digesting the testis it was found advisable to place 

 the gland in concentrated hydrochloric acid for 6 or 8 hours in 

 order to soften the tough fibrous albuginea. This was followed 

 by a digestion at 38 degrees C. in the thermostat with pepsin and 



^Mall, F. P. A Study of the Structural Uuit of the Liver. Am. Jour. 

 Anat., Vol. 5, No. 3. 



