786 EXPERIMENT STATION RECORD. 



The author boliovos spotted fever to be ui;initaiiiecl as follows: A certain per- 

 centage of the female ticks which have acquired the disease as a consequence 

 of feeding on animals which have been infected by other ticks, transmit the dis- 

 ease to their offsi)ring tlirough the egg. The new generation during the process 

 of feeding transfers the virus to certain of the susceptible small wild animals 

 (ground squirrels, rock squirrels, chipmunks, ground hogs, and perhaps others), 

 and this may take place during either the larval, nymphal, or adult stage, 

 hence at various times of the year. During the infection of the wild animals it 

 is required that hitherto normal ticks, either as larvae, nymphs, or adults, ac- 

 quire the disease by feeding simultaneously with, or shortly after, the feeding of 

 the infected ticks. Itegardless of the tick's stage of development at the time 

 it acquire<l the disease, the virus is retained into the adult period, and in certain 

 of the females reaches the germ cells and again appears in the next generation. 



The presence of tubercle bacilli in the circulating blood in clinical and 

 experimental tuberculosis. — The viability of the tubercle bacillus, J. F. 

 Anderson and M. J. Rosknau {Puh. Health and Mar. Hasp. Scrv. U. S.. Hyg. 

 LaJ). Bid. 51, pp. Ji2). — From 48 cases of human tuberculosis, glycerin-potato 

 cultures, guinea-pig inoculations, and smears were made from the sediment 

 obtained by centrifugation of blood, but in not a single instance were tubercle 

 bacilli demonstrated. In one instance the smears showed an organism that had 

 the morphological and tinctorial appearances of tubercle bacilli, but the glycerin- 

 potato culture and guinea-pig inoculations wei'e negative. 



" Tubercle bacilli were demonstrated in the blood of 7 of the 8 rabbits ex- 

 periujentally infected. In 3 of the 7 they were found both by cultures and by 

 animal inoculations. From this it would seem that when rabbits are infected 

 by subcutaneous inoculation of tubercle bacilli the latter are found in the circu- 

 lating blood in a large in-oportion of the cases, but not in sufficient numbers to 

 be detected in smears. It is of especial interest to note that the blood of a rab- 

 bit which at the autopsy did not present any naked-eye evidences of tuberculosis 

 was infective for a guinea pig. Tubercle bacilli were found in the blood of 

 only 1 guinea pig experimentally infected. It seems, therefore, that whereas 

 tubercle bacilli are frequently found in the blood of tubercular rabbits, it is 

 unusual to find them in the blood of tubercular guinea pigs and humans in 

 numbers or virulence sufficient to infect fresh animals."' 



In part 2, the viability of the tubercle bacillus is discussed at some length. 

 The results of investigations by various authors of the thermal death point of 

 the tubercle bacillus, its viability in dried sputum under different conditions, 

 the effect of sunlight upon it, and the period during which it remains virulent 

 in water, etc., are brought together in tabular form. " We have no easy method 

 of determining the death of the tubercle bacillus ; its virulence fades before it 

 dies. The criterion of death depends upon animal experimentation. The 

 tubercle bacillue may be classed with the nouspore-bearing organisms so far as 

 its viability is concerned. It is doubtful whether the waxy substance protects 

 the bacillus against external harmful influences to any unusual extent. The 

 thermal death point is 60° C. for 20 minutes. This is much less than was once 

 considered." 



A bibliograi)hy of the articles consulted is appended. 



A contribution to the study of the ophthalmic reaction of cattle to tuber- 

 culin, O. Bellini {Arch. 8cL R. Soc. Accad. Yet. JtaL. 7 (1909), No. 1-2, pp. 

 1-12; ah>i. in Rev. Gen. Med. Yet., 15 {1910), No. 110, pp. 81-89).— Ot 200 bovines 

 which were given the ophthalmic test at the abattoir at Mantoue, Italy, 29 gave 

 positive reactions. All the animals were given a careful post-mortem examina- 

 tion, when the 29 reactors were found to be affected, as were also 3 of the 

 animals which had not been detected during the test. The author is of the 



