The Microscope. * 71 



a bottle of ammonia in this way fifteen days in a warm room, and find 

 it much improved. The stain or color has a mild and beautiful 

 shade, not so harsh on the eyes as the more flashy, blazing colors, 

 while the vegetable cells retain their natural form. Stains having too 

 much ammonia or acid contract, distort and shrink the vegetable cells 

 more or less out of their natural form, especially delicate sections, and 

 cut them so that they are too fi'ail to handle with the greatest of 

 care, and are useless as specimens for scientific purposes. This is a 

 test for stains when they have too much ammonia or strong acid. The 

 latter can be improved by adding ammonia carmine to it, which has 

 been deprived of an excess of ammonia until the acid in the stain is 

 sufficiently diluted with the aqueous solution of ammonia carmine. . 



When sections have a very feeble affinity for green stains. I have 

 mounted sections in an aqueous mounting medium, made as follows: 



A syrup of white sugar, filtered, 1 oz. ; from ten to thirty drops 

 of pure glycerine. Mix thoroughly. The glycerine is added to pre- 

 vent the sugar crystalizing and getting brittle and flinty. The section 

 when stained is clarified in pure glycerine, and surplus washed off 

 with water, and the latter evaporated and then mounted in the syrup. 

 I have some nice mounts made in this way. To avoid bubbles, the 

 syrup should not be very thick. 



THE STRUCTURE OF TEETH. 



C. H. STOWEI.L, M. D. 



IN the September number of this journal is an article from me 

 on the structure of the human tooth. I now believe there are 

 some errors in my statements as given on page 196. 



I am convinced that the dentinal fibres are true processes from 

 the odontoblasts, and that the processes from the deeper cells do not 

 enter the dentinal canals. I further believe that these odontoblasts 

 are concerned, as stated before, in the formation of the dentinal 

 matrix ; and that they are capable of transmitting nerve impulses. 

 These odontoblasts are in direct union, or contact, with nerve fibrils. 

 The odontoblasts, with their processes— the dentinal fibres — are there- 

 fore, physiologically speaking, the endings of the dental nerves. In 

 brief, the correction I wish to make, is that the dentinal fibres are 

 processes of the odontoblasts — Klein notwithstanding; and that the 

 dentinal canals contain only their lining membrane, and the processes 

 from the odontoblasts. These processes do not quite fill the canals: 

 there is room for a flow of lymph around them, corresponding in 

 this regard to the lymph, canalicular system of cartilage and bone. 



