THE NERVOUS CYTOLOGY OF PERIPLANETA ORIENTALIS. 347 



(2) The teased cells were first stained with a 0.5% solution of methylen blue, 

 then flooded with a saturated solution of ammonium molybdate, and then with 

 Bethe's solution Number 3 (see Bethe, '96, p. 444). They were eventually dehy- 

 drated and mounted in the regular manner. The ammonium molybdate solution 

 was best applied as a hanging drop, for crystals tend to separate out, and if they are 

 allowed to settle on the specimen they are difficult to remove. 



In order to observe, if possible, the action of the methods of fixation previously 

 described, a group of fresh cells under the microscope were flooded with Lang's 

 solution. Instantaneous shrinkage and distortion occurred, and a few cells whose 

 margins had apparently become adherent to the slide exhibited appearances strik- 

 ingly similar to those of fixed preparations (PL XXVII, Fig. 29). 



IX. INTRA-VITAM STAINING. 



Three attempts were made to stain the cells during the animal's life. They 

 all failed completely. They were as follows: 



i. Technique. — (1) Two minims of a solution of three parts physiological salt 

 solution and one part polychrome were injected through a hypodermic needle into 

 the back of a cockroach; one and a quarter hours later decapitation was performed; 

 the body-cavity, containing the dye, was laid open and the animal was put in an 

 ice-box for twelve hours. The ganglia were then teased and examined. 



(2) Ten minims of a solution of equal parts of physiological salt solution and 

 Van Gieson's blue were injected through the ventral wall of a cockroach; one hour 

 and ten minutes later the animal was killed, and the body-cavity was found full of 

 the dye. The ganglia were teased out and examined at once. 



(3) A roach was fed on molasses containing a considerable amount of Nissl's 

 methylen-blue solution, and four and one-half hours after eating this the animal was 

 killed. The anterior end of the alimentary tract contained some of the blue dye; 

 two ganglia were fixed and sectioned and the other was teased. 



It was now necessary to obtain a method for preserving the cells as nearly as 

 possible in the condition seen in the fresh specimens, in order that they might be 

 studied in section. Three methods were tried. 



