Treponema pallidum in the Rabbit. 165 



by the recovery of the organisms in isolated instances from the 

 blood, lymphnodes or other organs as well as by the occasional 

 occurrence of generalized lesions in infected animals. However, 

 there is no evidence to show either the time or frequency with 

 which this dissemination occurs or whether the organisms thus 

 distributed over the body are capable of sustaining the infection 

 in these animals. 



With these questions in mind, a series of experiments was 

 undertaken, the object of which was to determine the frequency 

 of invasion of the regional lymphatics and the general circulation 

 following inoculation in the scrotum or testicles and how soon a 

 self-sustaining generalized infection might be established. 



Time and Frequency of Invasion of Regional Lymphatics. — 

 An examination was made of the inguinal lymphnodes in a series 

 of 29 rabbits which had been inoculated by the introduction of a 

 bit of infected tissue beneath the skin of the scrotum. The nodes 

 were excised under ether anesthesia at intervals of from 61 days 

 down to 48 hours after inoculation and the presence or absence 

 of Treponema pallidum determined by dark field examination or by 

 animal inoculation. 



The first group of nodes studied included those showing well 

 marked enlargement and induration and these gave positive 

 results in all cases. Nodes were then taken 5 days after inocula- 

 tion and after the lapse of only 48 hours. Positive results were 

 again obtained in all cases. 



Invasion of the Blood Stream. — A similar series of experiments 

 was carried out to determine the time and frequency of blood 

 stream invasion and something of the character of the blood 

 stream infection with relation to processes of reaction in the pri- 

 mary lesions. With a few exceptions, the animals used for these 

 experiments were inoculated in the testicles. The mode of deter- 

 mining the presence of Treponema pallidum in the blood of infected 

 animals was by bleeding from the heart, defibrinating and injecting 

 0.5 c.c. of blood into each testicle of 2 normal rabbits. 



A total of 81 bleedings was made on a series of 37 rabbits at 

 intervals of from 7 to 99 days after inoculation. The earlier 

 bleedings were all spaced with reference to some phase of the 

 testicular infection and from these it was found that organisms 



