ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
515 
Moller’s law with regard to the multiplication of the frustules, which 
prevails in Melosira, is certainly not true of all diatoms. In artificial 
cultures the propagation by means of auxospores can readily be followed 
out in many species of diatom, both filamentous and solitary. The 
restoration of form takes place habitually without the production of 
spores or sporanges. The protoplasm of the microfrustules escapes from 
the valves, and, at first enclosed in a membrane of cellulose, assumes first 
of all an irregular form, which gradually approaches that of the normal 
megafrustules. These primordial megafrustules acquire their regularity 
by bipartitions which immediately begin to take place in them. 
Whether the microfrustules are fertilized before germination must re- 
main at present undecided. 
j8. Schizomycetes. 
Effect of High Temperatures on Tubercle Bacilli.* — Drs. Forster 
and Bonlioff, though working quite independently, have examined the 
effect of temperatures below boiling point on tubercle bacilli. In 
Forster’s experiments the temperatures ranged between 40° and 95°, and 
Bonhoff ’s from 50° to 80°. The object of the former was to ascertain if 
the pasteurization of milk effectively destroyed tubercle bacilli contained 
therein. 
Both authors inoculated guinea-pigs in the peritoneal sac to demon- 
strate presence of living tubercle bacilli. Forster employed tuberculosis 
milk of cows, crushed tubercle and tuberculous sputum, while Bonhoff 
used pure cultivation of tubercle bacilli in calf’s lung broth with 4 per 
cent, of glycerin. On this medium the growth was extremely luxuriant 
in 10-14 days. Forster heated the tuberculous fluids enclosed in 
capillary tubes on a water-bath ; Bonhoff simply heated the pure cultiva- 
tions in a water-bath. 
The results of both authors are pretty well in accord. According to 
Forster, tubercle bacilli are killed when heated from 45-60 minutes at 
60°, according to Bonhoff it only takes 20 minutes. At 70° they die in 
6-10 minutes, while at 50° this result is not attained in 12 hours. 
Bonhoff noticed that the inguinal glands of animals which had been 
injected with cultures heated for 20 minutes at 60° underwent a slight 
enlargement. 
Origin and Presence of Alexins in the Organism.!— In an inter- 
esting and speculative paper Mr. E. H. Hankin suggests that the source 
of alexins, those substances which are the cause of the bactericidal 
power of the blood-plasma, is to be found in the eosinophilous granules 
in certain leucocytes. The hypothesis assumes a germicidal property 
existing in white corpuscles and blood-plasma, and the presence of special 
proteid substances, and endeavours to reconcile the opposing theories of 
Phagocytosis and Humoralism by showing that alexins are secretions 
from and by leucocytes. 
What are those bright highly refracting granules with greenish 
reflex and a love for eosin? They are the source from which the defen- 
* Hygien. Rundschau, ii. (1892) pp. 869 and 1009. See Centralbl. f. Bakteriol. 
u. Parasitenk., xiii. (1893) pp. 293-4. 
t Centralbl. f. Bakteriol. u. Parasitenk., xii. (1892) pp. 777-83, 809-24 (6 fi^g.). 
