ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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from the vein or chokes the cannula, tlio artery is tried. In this way 
a large quantity of perfectly germ-free blood is obtained. 
The flasks containing the blood are to be kept in a cool place, and 
by the next day the pale red clear serum has separated. This is removed 
from the flasks into similar vessels by siphoning the serum from a first 
flask into another empty one. Air contamination is prevented during this 
procedure by joining the flasks with a rubber tube, which passes by the 
intervention of glass tubing through the stopper of one vessel into that 
of the other. The end of this tube dips into the serum of the first tube. 
Each stopper has another perforation through which passes a glass tube 
plugged with cotton wool for filtering the air. If the blood have been 
carefully taken, and the vessels filled without a mistake, serum thus 
obtained can be kept for a long time. The quantity of blood obtainable 
from a lamb weighing 50-60 lbs. amounts to 2-2J litres, and the blood- 
serum from this is about 700-800 ccm. 
In order to distribute the serum into test-tubes without being con- 
taminated, the author uses the following apparatus. A burette, the 
upper opening of which is stopped with cotton wool, is connected below 
with a glass Y-tube, the other two arms of which are joined by clamped 
rubber tubes; one of these is long and connects with the glass tube 
dipping into a serum flask. The serum from the flask is put into the 
burette by siphon action and when a sufficient quantity is obtained 
the connecting tube is clamped, and then the other tube from which the 
tubes are to be filled is unclamped, and so on. 
(2) Preparing- Objects. 
Technique for Studying Tubercle Bacilli in Lung.* — Dr. A. Borrel, 
who has been studying pulmonary tuberculosis after intravenous injection, 
recommends as fixative saturated aqueous solution of sublimate to which 
5 per cent, glacial acetic acid has been added, or a mixture of sublimate 
and Flemming’s fluid. The whole of the lungs are immersed for five or 
six hours in the fixative, they are then incised to aid the penetration of 
the fluid. Fixation is complete in about 12 hours. From the sublimate 
the pieces are transferred at intervals of 24 hours to alcohols of in- 
creasing strength (50, 80, 96, 100), after which they are immersed 
in toluene for 24 hours, then in a mixture of equal parts of 
paraffin and toluene and finally in paraffin. The sections are fixed to 
the slide and stained by a method devised by Kiihne of Wiesbaden, not 
published but communicated orally to the author. It consists in using 
hydrochlorate of anilin (salzsaures Anilin) as a decolorant, and its special 
advantages are that it is less harmful to the tissues than acids, and while 
it will decolorize the tissues in a few seconds it does not remove the 
stain from tubercle bacilli. The preparations are stained for 10— 
15 minutes in Ziehl’s solution and then treated with an aqueous 2 per 
cent, solution of anilin hydrochlorate. They are then differentiated 
and dehydrated in alcohol and mounted in balsam, or the following 
procedure may be adopted : — (1) Stain the sections in haematoxylin or 
better still in haematein. The latter is preferable and the solution is 
thus made : — (A) dissolve 50 grm. of alum in 1000 grm. water by aid 
* Ann. Inst. Pasteur, vii. (1893) pp. 593-627 (3 pis.). 
2 E 
1894 
