and Laboratory Methods. 2651 



should be placed in the abdominal aorta with the mouth just above the coeliac 

 axis when injecting the thoracic viscera and head and neck, and low down in 

 the thoracic aorta when injecting the abdominal viscera. In either case the 

 vena cava should be opened either above or below the liver. It is best to place 

 a block under the back of the animal to insure a free venous outflow. 



If the animal is rare or valuable, a double canula may be placed in the 

 abdominal aorta and the whole animal injected at once. After such an injection 

 the whole animal, or the part injected may be left over night in 67 per cent, 

 alcohol and then removed to 82 per cent, alcohol, which should be changed a 

 few times. Thus a great deal of tissue, excellently prepared in a very short 

 time, may be had on hand for any emergency. 



The inner ear of a guinea pig fixed by HgCU injection gives a rarely fine 

 picture on section. After decalcification the cochlea should be laid open by a 

 section passing through the modiolus. This permits better infiltration and 

 imbedding, with the result that the delicate membranes are held in position by 

 the celloidin when cut and do not present the appearance so often seen of hav- 

 ing been dragged. 



Tincture of iodine added to the 67 per cent, alcohol used in washing out the 

 HgClj showed no noticeable advantage. 



A very valuable use of the method is in the preserving of brain tissue. A 

 brain may be fixed in situ by formalin injection, and then removed, the brain 

 stem cut out and placed in potassium dichromate solutions preparatory to sec- 

 tioning and staining by the Weigert-Pal method. Those who have had the dis- 

 appointment of having such post mortem changes take place in the inner cap- 

 sule and pyramidal tracts, before the penetration of the fixer, as to render the 

 tissue useless, will appreciate the value of this procedure. 



Though many uses of the method have been noted they are but a part of the 

 many ways in which the method was found very valuable in the Anatomical 

 Laboratory of the Johns Hopkins University during the past year. 

 Dept. of Anatomy, Indiana University. BuRTON D. MvERS. 



Differentiating Colonies of Typhoid, Colon and Allied Bacteria. — 

 Hiss has shown that it is possible by a very simple modification of ordinary 

 culture media to differentiate the colonies of the typhoid bacillus and the colon 

 bacillus upon ordinary plates. The media which he uses for this purpose are 

 several in number. All of them, however, contain agar, and they are quite 

 similar to the ordinary nutrient media. For example, the one upon which the 

 largest amount of work has been done is made up of agar, 15 grammes ; gelatine, 

 15 grammes; Liebig's extract, 5 grammes; dextrose, 10 grammes; water, 1000 

 c. c. This material, as will be seen, differs from the ordinary nutrient agar in 

 hardly any point, except that the peptone is omitted. In the other media which 

 he describes the peptone is in a similar manner always omitted. Using these 

 media for cultivating typhoid and colon bacilli, Hiss finds the two species very 

 readily differentiated. The typhoid bacillus produces a colony considerably 

 smaller than the colon, and it also develops, after proper growth, an abundance 

 of irregular filaments radiating from a central colony, whereas the colon bacillus 

 produces a colony with a uniform outline. This filamentous condition is a very 

 ready means of differentiation of the two types of bacteria.^/(V//7/. Med. Research. 



