BUREAtJ OF ANIMAL INDUSTRY. 605 



October 21: 10,8^0 in 1". 



November 18: 235 in 1". „ ^ ^^ • tu i- -i i^ 



December 0: A few bacteria still present, as determmed by liquid cultm-es. 



January 4: Seventeen in 1"^*=. 



January 11: No gi'owth on plates. 



That the hacterium can be kept alive in clear river water for four 

 months and perliaps longer is a fact very significant in itself. When 

 we consider, moreover, that the added bacteria multiplied so that 

 each individual was represented by ten at the end of five days, the 

 hardiness of the bacterium is very evident. The danger from in- 

 fected streams into which feces from sick animals find their way is 

 thus proved beyond a doubt. 



The effect of simple drying on the bacterium of hog-cholera. — 

 The resistance 6f this microbe to various agencies, physical and chem- 

 ical, is likewise of considerable importance in determining the man- 

 ner of infection, the spread of epidemics, and the possible means within 

 reach of destroying the virus. In order to test its vitality when de- 

 prived of moisture the following experiments were carried out : 



January 19, 1886: A number of cover-glasses were heated in the Bunsen flame 

 and then placed on a flamed glass plate under a flamed funnel. The mouth of the 

 funnel was plugged with cotton wool to allow desiccation wliile excluding aerial 

 organisms. When cool a drop from a pure liquid culture of the bacterium was placed 

 on each cover Avith a pipette, and the whole left in the laboratory at a temperature 

 of 65^^ to 80" F. Tlie culture used had been prepared January 7 from the fifth spleen 

 culture, hence was twelve days old. 



January 21: Two tubes of nutritive liquid inoculated by dropping a cover-glass 

 into each. Both turbid next day, containing the bacterium of hog-cholera only. 



January 25: Two tubes inoculated in the same way. Same result next day. 



January 28: Two additional tubes receive each a cover-glass. They were still 

 clear on the following day. 



January 29: Two tubes inoculated. 



January 30: One tube. These five tubes remained permanently clear. In one, 

 inoculated January 29, a fungus had developed from the cover-glass in the bottom 

 of the liquid. This, however, remained clear. 



This series placed the death-point of the bacterium between the seventh and the 

 ninth day. 



A second series of covers received each one drop from a culture obtained from a 

 mouse which had died from the effect of inoculation. The culture in beef infusion 

 I>eptone was ten days old. Treated in the same manner as in the preceding experi- 

 ment, the bacteria were found to resist drying for ten days, when the stock of cover- 

 glasses was exhausted. 



To determine whether bacteria in the body of the diseased animal possess a greater 

 power of resistance than those in cultures the following experiments were made: 

 Some bits of the spleen of a pig which was found crowded with the specific bacteria 

 of hog-cliolera were dried on sterile cover-glasses as above described, and then 

 dropped into tubes containing beef infusion. Cover-glasses which had been dried 

 for from eight to sixteen days were able to develop pure cultures of the bacterium 

 in the tubes. The stock of covers being exhausted, another series was tried in the 

 same way. The blood of spleen tissue was permitted to dry undisturbed until the 

 seventh day, when the first tube was inoculated. Cover-glasses dropped into cult- 

 ures on the seventeenth, nineteenth, twentieth, twenty-first, twenty-fourth, and 

 twenty-sixth days left the cultures sterile. Those dropped in on the eighteenth and 

 twenty-second days produced pure cultures of the bacterium. These experiments 

 indicate a greater resistance of the bacterium in spleen tissue, "which may live twenty- 

 two days in a dry atmosphere at a temperature of 70° to 80" F. 



On May 8 five cover-glasses upon which bits of spleen tissue, known to contain 

 the bacterium of hog-cholera, had been dried under a plugged funnel since March 

 20, were dropped into tubes of beef infusion. On the following day all tubes were 

 turbid. In one of them bacillus subtilis was present. All the others were pure 

 cultures, as determined by microscopical examination. Two of these were tested 

 furthermore on gelatine plates with the same results. This indicates that in the 

 varying teinperature of a room desiccation of small bits of tissue (not so large as a 

 pin's head) failed to destroy the bacterium in forty-nine days. In the experiments 

 with dried cultures those ten and eleven days old were chosen, so that if any resist- 



