484, EDGAR J. ALLEN. 
surface, the anterior gastric muscles were carefully cut through, 
as much of the green gland as possible removed with forceps, 
and the brain freed in front from the carapace. The whole of 
the head in front of the mouth was then cut off with a pair of 
stout scissors, and the anterior thoracic ganglion exposed from 
the ventral surface. When this has been done the whole 
stomach can be removed with the cesophageal nerve-ring 
attached. In some cases the thoracic ganglion was not 
dissected out, the commissures being simply cut across as far 
back as possible. The stomach thus removed from the animal 
was then placed in normal salt solution, and its anterior face, 
with the cesophagus and the anterior gastric muscles attached, 
cut off. After the esophagus had been slit longitudinally along 
its posterior wall, the whole piece thus obtained was spread out 
on a slide with the nerve-ring lying uppermost. The prepara- 
tion was then covered with a dilute solution of methylene blue 
in normal salt solution. In order to keep the tissue properly 
covered, it is an advantage to have a glass or metal cell attached 
to the slide. The strength of methylene blue found most use- 
ful was from 1: 50,000 to 1: 10,000. It is often good to start 
with the more dilute solution, and gradually add the stronger 
as the staining proceeds. In cold weather the slide should be 
kept warm; indeed, the staining always takes place more 
rapidly at a temperature of 25°—30° C. 
One great advantage of this method, due largely to Bieder- 
mann! and Apathy,” over the original method of Ehrlich, lies 
in the fact that the object can be examined with the micro- 
scope from time to time, and the staining process watched. 
When the staining is at its best it may be fixed by placing the 
tissue in a solution of ammonium picrate containing excess of 
ammonium carbonate (Apéthy), and, after a few hours, mount- 
ing in glycerine mixed with an equal volume of the fixing 
solution To obtain good preparations a great deal depends 
1 Bieaermann, “ Uber den Ursprung und die Eudigungsweise der Nerven 
in den Ganglien wirbelloser Thiere,” ‘Jena. Zeitschr.,’ Bd. xxv, 1891. 
2 Apathy, “Erfahrung in der Behandlung des Nervensystems fiir histo- 
logische Zwecke,” ‘ Zeitsch, wiss. Mikr.,’ Bd. ix, 1892, 
