31(3 G. B. WISLOCKI AND T. J. PUTNAM 



cyanide and citrate solutions as Prussian blue. The brains 

 which had been injected with trypan blue w^ere fixed in 10 per 

 cent formalin without the addition of acid. The fixation was 

 accomplished by inmiersion, in order to avoid the disturbing 

 factors of intra-arterial injection. 



On gross inspection, the surfaces of the brains were found 

 either unstained or very faintly colored. On cutting thin coronal 



o 



Fig. 1 Cross-section of the brain of a young rabbit in which dilatation of the 

 ventricles had resulted from the injection of lampblack into the cisterna cerebello- 

 medullaris. Subsequently a solution of potassium ferrocyanide and iron ammo- 

 nium citrate was injected by replacement into a lateral ventricle. The animal 

 was killed two hours later and the brain fixed. A zone of Prussian-blue-stained 

 brain tissue can be seen surrounding the ventricles. 



Fig. 2 Cross-section of the brain of a young rabbit in which dilatation of the 

 ventricles has been similarly brought about. Trypan blue was injected into the 

 ventricles of this animal. A zone of stained tissue can be seen surrounding the 

 ventricles. The insert shows a section of the lumbar cord from the same animal. 

 The wall of the central canal and a zone of tissue surrounding it are faintly stained. 



Fig. 3 Cross-section of the brain of a young cat, showing the dilated ventricles 

 into which a solution of potassium ferrocyanide and iron ammonium citrate 

 was injected. A zone of Prussian-blue-stained tissue is seen surrounding the 

 ventricles. 



sections of the brains and cords a striking appearance was dis- 

 closed. The ventricles, as was expected, showed varying degrees 

 of distention. The walls of the ventricles and a zone of surround- 

 ing brain tissue to a depth of several millimeters were deeply 

 stained (figs. 1, 2, and 3). This zone of staining enclosed not 

 only the lateral and third ventricles, but the aqueduct of Sylvius, 

 the fourth ventricle and central canal of the cord, demonstrating 

 a free communication between all of the cerebral ventricles and 



