METHODS I'OR PREPARING THE ORGAN OF CORTI, 375 



the organ of taste, and Corti's organ, are omitted entirely. 

 Surely this latter, at least, is of as great importance and in- 

 terest as the retina. It is generally, I imagine, considered 

 very difficult to demonstrate ; and such is, as far as regards 

 the finer relations and structure of its several components, 

 undoubtedly the case, and in these particulars it is one of 

 the most difficult of histological problems ; but a great deal 

 can be seen with comparative ease, and, as I have had con- 

 siderable experience in the matter, I propose here to give 

 some notes on the subject. I do not consider them to be by 

 any means exhaustive or novel ; but I have always found 

 microscopists very anxious to see preparations of Corti's organ, 

 and very commonly unacquainted with the methods by which 

 they may be obtained, and anxious to be informed concerning 

 them. 



As in most histological investigations, the methods to be 

 adopted fall under two heads. Firstly, those by which 

 preparations may be obtained, which demonstrate the general 

 and coarser relations of the several parts of the whole organ ; 

 that is, sections through the entire cochlea with all the parts 

 in situ. Secondly, those in which the finer structural and 

 more intimate connection of these several parts may be ob- 

 served, which more delicate points are, unfortunately, not to 

 be made out from the former class of preparations, because 

 the reagents which we are obliged to employ in their produc- 

 tion alter and in a great measure destroy the finer tissues. 



The more delicate structure must be studied in small 

 portions of the organ, immersed in the fresh state in neutral 

 fluids, or treated with such reagents as iodized serum or 

 osmic acid. 



The most convenient cochlea for the making of the first 

 class of preparations is that of the guinea-pig, though the 

 methods here to be described are applicable to any cochlese ; 

 and I have thus made sections from the hedgehog, cat, dog, 

 rabbit, rat, and human subject. A guinea-pig should be 

 killed, and, whilst it is still warm, the head severed from the 

 body, the lower jaw should be disarticulated, and the two 

 tympanic bullae exposed. On one of the bullae being opened 

 the cochlea Avill be seen projecting into the cavity, looking 

 like a small conical spiral shell. It is free, and not more or 

 less imbedded in the petrous bone, as is the case in most 

 mammalia, and it is this peculiarity which renders the guinea- 

 pig so convenient for the study of Corti's organ. The cochlea 

 should be removed entire, the membranes closing the open- 

 ings to the scalfe broken away, and the organ should be placed 

 in a considerable volume of half per cent, solution of chromic 



