402 HOST-PARASITE RELATIONSHIPS 



intraperitoneally. Returning to the role of leucocytes, the mere presence of large 

 numbers may be a detriment unless the cells are effective in digesting bacteria. 

 Otherwise they serve merely as a means of disseminating the pathogen throughout the 

 host. These studies illustrate the wisdom of Dr. Gowen's approach, namely to deal 

 with resistance as an entity. Work in his laboratory revealed that there are genetic 

 differences in ability of leucocytes 69 and macrophages 949 to digest phagocytized 

 bacteria. The Camp Detrick work with anthrax 1375 has also demonstrated the 

 importance of qualitative differences in leucocytes. 



The technique of double matings was mentioned by Dr. Gowen. This tool for 

 investigation has not been fully exploited. We have found in our laboratory that about 

 one litter out of 10 to 15 matings is of mixed parentage, when females are placed with 

 pairs of males. All that is necessary to determine parentage is to have suitable color 

 markers. When the seminal vesicles of one male are removed, to prevent plug forma- 

 tion, the number of mixed litters is not increased as might be expected. We have had 

 fewer mixed litters by this procedure. Direct observation has shown that mixed litters 

 are usually the result of a rapid round robin, with one male providing sperm and no 

 plug or only a partially formed plug. Dominance (in the behavioral sense) of one male 

 over the other has no effect on the percentage of mixed litters. 



The experimental work with murine typhoid has a practical aspect. It is note- 

 worthy that in Dr. Gowen's laboratory, even though the precautions are not elaborate, 

 there has never been an outbreak of typhoid in the breeding colony. Mice and Sal- 

 monella do not necessarily go together, like pie and cheese. In our own laboratory 

 murine typhoid was introduced by mice from elsewhere. Until efforts to eliminate the 

 pathogen were successful, the disease remained confined to the imports and their 

 descendants. Except in the few cases in which crosses were made, our own laboratory 

 stocks remained free from disease. 



At present there is a trend toward team research involving more or less intimate 

 cooperation between workers in different disciplines. This is desirable and will no 

 doubt increase. However, there will always be a place for an energetic, imaginative, 

 and well-rounded independent investigator. May Dr. Gowen continue for many 

 years to produce the type of research that he has described. 



Dr. Gordon: In considering methodology in this field, I would like to take just a 

 minute or two to mention work of one of my colleagues at the Naval Medical Research 

 Institute, Bethesda. 621 Dr. Herbert S. Hurlbut's interest is in the transmission of 

 arthropod-borne viruses, and he has determined the susceptibility of other arthropods 

 than the ones naturally involved in transmission, using representative viruses of this 

 arthropod-borne group. That is, he took arthropods such as house flies, a species of 

 Lepidoptera, beetles, Hemiptera (all non-blood-sucking), and some hemophagous arthro- 

 pods, and determined their susceptibility to the selected viruses by inoculation through 

 the body wall with a capillary pipette. He found that many of these species were 

 susceptible in the sense that they would propagate the virus, it could be recovered in 

 fairly high titer in some cases, and could be transmitted from one individual to another 



