234: THE AMERICAN MONTHLY. [December. 



Experiments with Chitin Solvents.* 



By T. H. morgan. 



Dr. Loop in the Zoologischer Anzeigei' (1885, P- 333) stated that Laba- 

 raque solution (potassium hyperchlorite) or Javelle solution (sodium hyper- 

 chlorite) would completely dissolve the hardest chitin parts of insects, so that 

 they can be sectioned or so that staining fluids will penetrate them. The 

 author, in i8S7-'S8. made some experiments, the results of which he records 

 as follows : — 



It so happened that the first experiments were made upon the eggs of the 

 common cockroach, and the selection turned out to be a fortunate one. Many 

 eggs are laid at one time surrounded by a stifl' chitinous coat forming the so- 

 callefl raft. Two principal methods wei'e employed — one using the commer- 

 cial fluid full strength, the other diluting it five or six times. Rafts wei^e 

 placed in the weak Labaraque solution, left in till the chitin became soft 

 and transparent, taking, if the solution were slightly wari?ied. from thirty 

 minutes to an hour. If embryos are advanced, thev may now be taken from 

 the envelope one by one. If still young, they had better be hardened and cut 

 all together. In either case the embryos after washing were transfeired to 

 picro-sulphuric acid, thence through alcohol to 95 per cent., then imbedded 

 in paraffine cemented to the slide, and stained ' on the slide.' Corrosive sub- 

 limate or chromic acid were also used, but^vith less satisfactory results. The 

 embryos transferred directly from Javelle solution to alcohol were nearly as 

 good as those put through picro-sulphuric acid. 



To specimens already hardened and preserved the solvent may also be ap- 

 plied, but where material is obtainable fresh it should preferably be treated 

 immediately. 



In most cases the object should be stained on the slide after cutting, but if 

 the object be small it may be stained ifi toto after the chitin has been dissolved. 



The only difficulty met in using the Labaraque solution is that it not only 



attacks the chitin. but also the soft tissues, apparently the connective tissue. 



Thus the joints of insects' legs, unless great care be exercised, \vill fall apart. 



But this difficulty can be met bv removing the animal before the solution has 



g-one far enough for this, and bv diluting the solution. The onlv time when 



*^ ^ . " . . . " . 



the strong solution can be emploved is when the chitin wholly invests the 



substance to be cut. While this method will not serve in eveiy case where 



chitin prevents cutting of tissues, it can be extensivelv employed to overcome 



difficulties heretofore insuperable. 



NOTES. 



Baldness. — For the benefit of those who have discarded the *• stiff' hat' 

 from fear of baldness after all the recent utterances on that subject, it is inter- 

 esting to note from Popzilar Science Monthly the remark that the Parsees 

 of India are compelled to wear during the day a hat tight enough to crease 

 the scalp, and a skull cap at night, and yet he has never seen or heard of one 

 of them who was bald. 



Mr. S. H. Scudder, of Cambridge, Mass.. will shortly publish a mono- 

 graph on the butterflies of the Eastern United States. He has spent many 

 years in its preparation, having announced it in 1S69. It will be illustrated 

 with very numerous plates of the adults, caterpillars, eggs, nests, etc. — in all 

 2,000 figures. The work of printing the plates has been in progress for 3 

 years. It is to be out in January, 1889. — Science. 



* From Biological Studies, Johns Hopkins University, vol. iv, p. 217. 



