walling: the acridid^an heart. 363 



the Nissl stain and chrome-oxalic fixative of Graf, as de- 

 scribed by Houser. Graf used a mixture composed of 200 cc. 

 of an 8 per cent, aqueous solution of oxalic acid, 150 cc. 95 per 

 cent, alcohol and 150 cc. of aqueous solution of chromic acid. 

 The tissues were fixed about six hours and then washed out 

 with 70 per cent, alcohol, and sections made by the paraffin 

 method. 



The Nissl stain (methylen blue 3.75 grams, olive-oil soap 

 1.75 grams, and 1000 cc. distilled water) was poured steam- 

 ing-hot over the sections for about five minutes. Differentia- 

 tion was accomplished with anilin alcohol, and clearing with 

 oil of cajeput. 



The erythrosin mixture of Held, also mentioned by Houser, 

 gave good results as a counter-stain. 



Sections preserved for several months in 10 per cent, for- 

 malin were stained with the Nissl stain with good results. 



Van Gehuchten's fixing fluid, according to Hardesty (p. 98), 

 but using Nissl staining fluid and erythrosin for a counter- 

 stain, proved to be good, especially for connective tissue. 



The only fixatives that brought out the so-called "ganglion- 

 cells," however, were 10 per cent, formalin and mercuric 

 chlorid or formalin alone, and the chrome-oxalic fixatives. The 

 simple 95 per cent, alcohol fixation, as used by Nissl himself, 

 with the Nissl stain, gave good results, but the chrome-oxalic 

 solution was the more satisfactory. 



Sections through the ventral nerve-cord and the thoracic 

 and abdominal ganglia were made with the best methods, in 

 hopes that ganglion- and nerve-cells could be certainly identi- 

 fied and their structures compared with others found in the 

 heart, but satisfactory results were not obtained with any of 

 the many methods used. In fact, structures found in and 

 around the ventral cord did not any more resemble nerve- or 

 ganglion-cells, as we would expect to find them, than did those 

 found in the heart sections. For this reason it has certainly 

 not been proven that nerve- or ganglion-cells do not exist in 

 the grasshopper's heart. 



ANATOMY OF THE HEART. 



My observations corroborate in most respects the descrip- 

 tion of the circulatory system in insects, although very little 

 mention is made of the grasshopper. Graber^^ seems to have 

 made a sketch of a cross-section through the heart, but it is 



14. Graber, Folsom's Entomology, p. 125. 



