602 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
anilin dye is not directly utilised by the protoplasm, but by some 
dissociation product formed during the metabolic activity of the proto- 
plasm. 
Testing Butter and Milk for Tubercle Bacilli.* — Dr. Petri found, 
in 102 samples of butter, tubercle bacilli present in 32*3 per cent. The 
tuberculoid bacillus was also frequently present, both alone and in con- 
junction with the true tubercle bacillus. The test applied was to inject 
5 ccm. of the butter into guinea-pigs. The animals which succumbed 
w'ere carefully examined, and those which survived were killed and also 
inspected. If rodlets giving the characteristic staining reaction were 
found, further inoculations were made w’ith the suspected material. 
While the true tubercle bacillus invariably gave rise to infection, the 
tuberculoid rodlet failed to excite specific inflammatory changes, and the 
inoculation wound healed up perfectly. 
In 64 samples of milk, 14 per cent, contained tubercle bacilli and 
6 * 3 per cent, the tuberculoid rodlet. The milk used was centrifuged, 
and 3 ccm. of the cream, the buttermilk, and the sediment were injected 
into the peritoneal sac of four guinea-pigs. 
Black Hsematoxylin.f — Prof. F. A. J anssens recommends the follow- 
ing preparation of haematoxylin for biological work. It is prepared 
very much in the same way as Delafield's haematoxylin, the chief dif- 
ference being that iron-alum is substituted for ammonia-alum. To a 
hot saturated solution of ammonia-iron-alum (NH 4 ) 2 Fe 2 (S0 4 )4, are added 
4 grm. of haematoxylin dissolved in absolute alcohol. The soluble 
black dye which is thereby formed is allowed to stand for a while, and 
then 100 ccm. of glycerin and 100 ccm. of methyl-alcohol, CH 4 0, are 
added. 
Prodigiosin as Staining Reagent for Botanical Specimens.}: — Prodi- 
giosin, the pigment produced by Bacillus prodigiosus, is recommended by 
Herr O. Rosenberg as a useful reagent for staining cuticula, corky mem- 
branes, and fatty substances. To these it imparts a deep red colour, and 
though woody tissue and cell-contents are also faintly stained, they lose 
the stain when washed in alcohol. The pigment is obtained by culti- 
vating the microbe on potato at 25° for 3 or 4 days. The bacterial mass 
is then scraped off, placed in a glass vessel, and dissolved in 95 per cent, 
alcohol. The alcoholic extract when filtered is a clear brick-red fluid. 
For staining sections the strength recommended is 5 ccm. of the bacterial 
substance to 25-30 ccm. alcohol. Exposure to light damages the colour ; 
but if preserved in black bottles protected from light, the fluid will keep 
for a good time. The sections from fresh or preserved tissue are im- 
mersed in the fluid for 5 to 10 minutes, and on removal it is well to pass 
them through alcohol. The parts stained are cuticula and corky tissue, 
though the oil-drops in the hyphae of fungi take up the pigment freely. 
It is easy to double stain with prodigiosin, especially with malachite- 
green or chloranilin. In the former case the woody tissue is green ; in 
the latter yellow. 
* Arb. aus d. kaiserl. Gesundheitsamt, xiv. (1898) p. 1. See Zeitschr. f. angew. 
Mikr., iv. (1898) pp. 64-5. t La Cellule, xiv. (1898) p. 207. 
X Zeitschr. f. wiss. Mikr., xv. (1898) pp. 56-60. 
