PREPARING SECTIONS OF TEETH. 35 



histological text-books, and then filter twelve or fifteen drops in a 

 watch-glass, and add a few drops of distilled water ; stir well to 

 mix the agents. Place in a few sections (the fewer and the slower 

 they stain the better) from the spirit, and let them straighten out 

 on the stain, and then gently press under the logwood ; leave it 

 for about ten minutes (the time differs in every case), and then 

 test them by washing in tap water. This is about the only time 

 we have occasion to use anv other than distilled water, but the 

 former fixes the stain the best. When deep enough and well 

 washed to remove all precipitates, place the sections in spirit for a 

 good ten minutes to dehydrate, then in clove oil, and finally 

 mount in Canada balsam, or what other media is desired. All 

 the stains are used, with only slight modifications, in a similar 

 manner. 



Picro-Carmine is a very useful stain on account of its double- 

 staining property. Place the sections in a strong solution for from 

 ten to thirty minutes, then wash in acidulated water (distilled 

 water to which one or two drops of acetic or picric acid have been 

 added). Leave in this for fifteen to thirty minutes, wash quickly 

 in alcohol, and then transfer to clove oil and mount in balsam. 

 Some histologists are against the use of balsam as a medium, and 

 advise glycerine or Farrant's media. Logwood is a good combin- 

 ing stain with the above. Fuchsin is also a good stain. 



The Mexican jumping seed, or " Devil's bean," is a euphor- 

 biaceous plant of such poisonous properties, that it is used by the 

 Indians to envenom their arrow-points. It not having been scien- 

 tifically identified to satisfaction. Dr. C. V. Riley has made a special 

 study of it. The saltatory property is not intrinsic with it, but is 

 imparted to it by an insect {Carpocapra saltitans), which secures 

 lodgment within the bean and does the work. Dr. Riley believes 

 that the insect is developed in the capsules of several species of 

 the genus Sebastia?ia, 



