Literary Notices. xxix 



of the nerves may be fully laid down. This point, though not abso- 

 lutely necessary, is certainly a great advantage. The last condition 

 involves, fourth, quite rigorous decalcification in any bony fish. And 

 this is perhaps the point of chief difficulty, for not only must the tis- 

 sues, especially the medullated nerves, be well preserved during the 

 process of decalcification, but they must be left in such a chemical 

 condition as to be amenable to the Weigert reaction subsequendy. 

 Finally, one has to determine experimentally the particular combina- 

 tion of mordant, stain and decolorizer which will give the clearest re- 

 sults. 



The chemistry of the Weigert reactions has not, to my knowledge, 

 been sufficiently worked out to make it possible to predict in advance of 

 actual trial the result of any given combination of fixer, mordant, stain 

 and decolorizer; it is in the hope of sparing some other investigator the 

 weary drudgery of similar blind experimenting that the results of sev- 

 eral of my experiments are here published, though the number of fail- 

 ures far exceeds that of successful preparations. It is hoped, too, that 

 these data may be of value in understanding the nature of the Weigert 

 reaction and allied processes. 



The same general method of procedure, which has in my hands in 

 some cases given most excellent preparations, has been adhered to 

 throughout the series of experiments, and is to be understood as apply- 

 ing to each case unless otherwise stated. This procedure involves the 

 fixation and decalcification of the specimen entire or nearly so, in large 

 specimens one side of the head being sliced off" with a sharp knife and 

 scissors so as to open thoroughly the cranial cavity without injury to 

 the structures in the median line. The specimen is then dehydrated in 

 alcohols, cleared in cedar oil, embedded in paraffin and cut into serial 

 sections by means of a Minot microtome. Cedar oil is preferred to the 

 other clearing oils because, during the long sojourn which is sometimes 

 necessary, its effect is less injurious than that of any other clearing 

 agent. Previous to the embedding or during that process the specimens 

 should be aspirated with a two-way syringe or under, the receiver of a 

 good air pump to remove from the cavities of the body the gases evol- 

 ved during decalcification. If the aspiration is conducted during the 

 stay in cedar oil, the exhaustion should be carried on until the pressure 

 is measured by five to eight mm. of mercury and the specimen held at 

 this pressure for several minutes. By this process large specimens can 

 be permeated as thoroughly with paraffin as with celloidin, though of 

 course the times in all of the solutions, especially in the paraffin bath, 

 must be considerably prolonged. The ribbons may be mounted on the 



