walling: the acridid^an heart. 361 



but in no case did he find nerves in the heart or any connect- 

 ing the heart with the central nervous system. 



McClendon** found a nerve-cord on the dorsal side of the 

 heart of the scorpion, and Beyne,i" in his research on the ori- 

 gin of heart action, nervous or muscular, says that he found 

 no nerve-cells in the snail's heart. 



METHODS. 



The most serious diflficulty in connection with this research 

 was to obtain a method by which the heart-tissue could be re- 

 moved from the hard chitin and sectioned without injuring 

 the structures. 



The first method employed was to use decapitated speci- 

 mens, or dorsal sections, in which the viscera were removed 

 and the heart-tube left intact. Such specimens were placed 

 in the fixative for the required length of time, washed and run 

 through the necessary solutions, and embedded in paraffin. 

 When the paraffin had hardened the outer covering was cut 

 away, and with it the hard chitin. This method was very un- 

 satisfactory. The tissue became brittle and dry and chipped 

 away with the chitin, so that complete sections could not be 

 obtained. 



I finally hit upon a method that gave favorable results. 

 After exposing the contracting heart to view in its dorsal 

 chitin, a drop of 1 per cent, acetic acid containing methyl 

 green was placed upon the tissue, which at once stopped con- 

 tracting. As it was desired to examine this preparation under 

 the microscope, I tried to remove a section of it from the chitin 

 and to my surprise found that the whole delicate structure 

 could be entirely separated from the chitin by carefully lift- 

 ing one end of the soft tissue with the forceps and gently 

 scraping next to the chitinous surface with a scalpel. 



I then decapitated an animal and filled the body cavity with 

 the 1 per cent, acetic acid and found that in a short time, three 

 to five minutes, the whole body was so completely loosened 

 from its encasement that, by carefully cutting the chitin along 

 both sides and employing the scalpel, the entire body could be 

 removed, leaving the outer shell quite transparent and entirely 

 free from all of the body-tissue. Even the hard chitinous 

 structures extending into the thorax were loosened from their 

 tissues. 



9. McClendon, Biological Bulletin, 1904, VIII, p. 38. 



10. Beyne, .!., Zeutralblatt fiir Phys., Bd. XIX, No. 25, 1905, p. 959. 



