Eoss Granville Harrison 209 



was prevented from healing by the insertion of 'a hedge-hog spine for a 

 few hours, until the cut surfaces healed over. The hole made in this 

 way was found to remain open in the majority of instances, and the 

 spinal nerves were thus prevented from growing out into the limb. 

 Such larvae live readily for a time, but difficulty was experienced in keep- 

 ing them alive until the time for metamorphosis. One specimen lived, 

 nevertheless, for this length of time. As regards outward form the 

 hind legs developed fully; all of the segments were normal, as was the 

 number of toes. The limbs had, however, an atrophic appearance and no 

 voluntary movements were ever observed, nor could any response to 

 mechanical or electrical stimulation be obtained. Examination of sec- 

 tions failed to reveal the presence of nerves in the hind limb. Cartilage 

 bone and muscle were normally differentiated. The striated contractile 

 substances filled out the nerve fibers, which were, however, of somewhat 

 smaller calibre than in the fore leg in which the nerves were intact. 

 The individual muscles of the hind limb are clearly defined, but it has 

 not been made out as yet whether all of the muscles normally found in 

 the limb are present in this specimen also. The work will be continued 

 during the present season and a full account published by Mr. Lang- 

 necker. 



Tlie Development of the Einhrijo in Solutions of Acetone-cliloroform. 



For the purpose of drawing or carefully studying living tadpoles it 

 is nearly always necessary to anesthetize them. Acetone-chloroform has 

 been found to be exceedingly well adapted to this end.° It is very easy 

 to manage; a few small crystals added to a watch glass or small dish of 

 water containing the larvae suffice to stop all voluntary movements, in- 

 cluding those of respiration, within a few minutes, while the heartbeat 

 is scarcely affected. The narcosis may be continued as long as desired. 

 On transferring the tadpoles to fresh water recovery takes place quite as 

 rapidly as the narcotization did. 



These observations led to the experiment of rearing larvae under con- 

 tinued narcosie in order to determine the effect of their forced inactivity 

 upon the development of the musculature. It is certain that all func- 

 tional activity of the muscles is suspended during the action of the drug 

 and also that this is brought about by action upon the nerve centers and 

 not peripherally. 



'^ It was at the suggestion of Dr. Abel, who first discovered the anaesthetic 

 properties of acetone-chloroform, that I made use of this drug. Miss Ran- 

 dolph, oo, has shown that it is very useful for the narcotization of many kinds 

 of aquatic organisms. The substance is known commercially as " chloretone." 



