508 REPORT OF THE COMMISSIONER OF AGRICULTURE. , 



nous lieating at 58° 0. la the latter medium its growth remain^ limited 

 to the track of the uecdle, forming there a cylindrical body not more 

 than 1""™ thick after a number of we^ks. The lower, free end of this 

 slender plug is somewhat enlarged into a knob. On the surface of the 

 serum it spreads out as a very thin whitish layer. No liquefaction takes 

 place. 



Thermal dcath-jmint of the swine-plar/ue hacterium. — Four tubes were 

 exposed to a temperature of 58° to 60° C. for about two hours. Tliey 

 contaiued liquid cultures varying in age from one to four weeks. When 

 fresh tubes were afterwards inoculated from these, three remained 

 steiile, the fourth contained a bacillus. It was evident from this that 

 the bacterium had been destroyed. The presence of the bacilhis may 

 be accounted for by the w^ater of condensation formed in the up{)er por- 

 tion of the tube during the heating which had washed down some spore. 

 This experiment having been made for another purpose, the death-point 

 was again determined as follows : 



Two tubes eacli, cf nutritive liquid, (one, meat infusion witii onc-Jialf per cent, 

 sodium chloride, tlie other meat infusion -with 1 per cent, peptone), -were inoculated 

 from four pure liquid cultures from different animals and one, two, three, and four 

 weeks old respectively. Before inoculating the tubes they were raised to 58° C. 

 After inoculation they were esposed, four at a lime (one from each culture), to the 

 same temperature for ten minutes, then cooled off quickly in cold "vvator. Seven tubes 

 remained pennanontly clear, the remaining one, from a culture three weeks old, be- 

 came turbid on the fourth day and contained the bacterium which was introduced. 



The thermal death-i)oint must, therefore, bo set down at about 58° 0. 

 The fact that the cultures of all ages from one to four weeks succumbed 

 at this temperature, demonstrates the absence of any resistant spore 

 state, such as that tbund in bacilhis siibiilis and bacillus anthracis. 



It is a very imi)ortant point to determine whether the virulence of 

 pathogenic bacteria is lost during artificial cultivation. To determine 

 this point the following experiment deserves to bo recorded: 



A culture In beef infusion peptone, made December 7 from the si)leen 

 of pig No. 114, was used to inoculate a potato December 21 on wbicli it 

 grew at a temperature of 05° to 80° F. quite luxuriantly. January C, one 

 month after the microbe liad been taken from thebody, a liquid culture 

 was again i)repared from the material on the potato. On the following 

 day three mice (Nos. 37, 38, 39) received hypodermically 7, 5, and 3 drops, 

 respectively, of this liquid culture. No. 39 died January 10, Bladder 

 greatly distended, hemorrhagic spots over its surface. Slight ccchy- 

 mosis at the point of inoculation. No bacteria on cover-glass prepa- 

 rations of the spleen. As there was some doubt about this case no cult- 

 ures were made. Nos. 37 and 38 found dead January 14, one week 

 after iuoculation. Eoth had been sick for several days previous. In 

 •No. 37 there was a whitish degeneration of the muscular tissue at the 

 point of inoculation, and slight injection of the surrounding vessels. 

 Spleen slightly enlarged, almost bloodless, friable, crowded with the 

 bacterium of swine plague ; kidneys congested and containing the same 

 bncteria in large numbers. In No. 38 the lymphatic glands of the knee 

 fold very large ; spleen about 1 inch long, three-eighths of an inch 

 wide, and nearly one-fourth of an inch thick, very dark. It might have 

 been mistaken for a lobe of the liver it was so large. The vessels of a 

 part of the mesentery were distended with blood which had infiltrated 

 the tissues for a short distance around them. The bacterium of swine 

 ])lague was found in spleen and kidneys, other organs not examined. 

 Lungs in part deeply congested and sink in water. A liquid culture 

 from the heart's blood of each was turbid next day with the same bao- 

 torium injected. 



