550 Professor David James Hamilton [March 8, 



not exert its beneficial influence if administered by the mouth, and in 

 a condition fit to be absorbed. 



During the months in which the disease is rampant, however, the 

 protective influence of the intestinal wall is lost in a large proportion 

 of cases ; the organism gets over into the peritoneal sac, fructifies 

 within it, and kills the animal. 



The spores being voided with the dejecta are taken up from the 

 pasture by a fresh host, and the result seems to depend very much on 

 the season of the year at which this happens. Should it occur during 

 the susceptible months the danger is extreme, while, at other periods, 

 it is practically nil. Nevertheless, the younger the animal the more 

 liable is it to the disease, and hence we may suppose that the 

 ingestion of the organism at an early period must have effected its 

 immunisation. 



Cause of Periodicity of Lovinng-Ill. — The insusceptibility of the 

 sheep to the disease at certain times of the year seems to depend 

 directly or indirectly on the condition of its blood. The blood of the 

 sheep during the spring months of the year usually constitutes an 

 excellent medium of culture, while at other times it, as a rule, is not 

 only inimical to the growth of the bacillus of Looping-ill, but is 

 intensely bacteriolytic to it. So that if, say, the blood of the sheep 

 during the month of July, be mixed in vitro with a culture of the 

 bacillus, the mixture covered with olive oil, and the whole incubated 

 at a body temperature for twenty-four hours, probably every bacillus 

 will be found to have vanished. During the susceptible months, 

 however, the organism multiplies and spores on the blood of the 

 sheep perhaps better than upon any other medium. It is evidently 

 this inhibitive action on the part of the blood during most of the year 

 which prevents the organism growing upon it or upon the peritoneal 

 liquid, for there is no reason for believing that the organism gets 

 into the alimentary canal with more facility during the months in 

 which the sheep is susceptible than at other times. The peritoneal 

 liquid apparently does not possess solvent powers to anything like the 

 same extent as the blood, and where the bactericidal action of the 

 blood is lessened, as during the months of susceptibility, the organism 

 is enabled to pass the wall of the intestine, to fructify on the 

 peritoneal liquid, and to kill the animal acutely with all the symptoms 

 of toxic poisoning. The peritoneal liquid in such instiinces is thick 

 and turbid, and contains the organism in abundance. 



Cause of the Toxic PItenomeua. — It may happen, however, that in 

 other instances the blood still retains sulficient bacteriolytic properties 

 to dissolve any of the organism which gets into it, altliough it is not 

 sufficiently inhibitive to prevent a certain exodus of the bacillus from 

 the intestine. Those bacilli which enter the blood stream, under 

 these circumstances, are still bacteriolysed, and apparently the same 

 thing happens, but to a minor extent, within the peritoneum. The 

 blood in such animals will be found free from bacilli and the 



