462 DISEASES OF bWINE 



for wagons hauling diseased and exposed hogs to pass along these 

 same roadways and leave behing them a trail of infected bedding, 

 manure, and other disease-carrying material. These young pigs, 

 in rooting around, come in contact with the disease-carrying sub- 

 stances, and it is not long until they begin to show signs of the 

 disease. An outbreak that sweeps through the entire herd soon 

 follows. 



The much higher death-rate which occurred in the sucking 

 pigs as compared with the older shoats is also a common occur- 

 rence in cholera. The younger the animals, the more easily they 

 become infected, and also the more easily do they die from the 

 disease once it makes a start in the herd. 



In connection with the results of the outbreak in the treated 

 animals there are also some points that help to make clear a 

 number of things which have been already said about the use of 

 serum. 



In these animals we again find that double the usual dose of 

 virulent blood with even a little less than the usual dose of serum 

 was used, and yet no bad results followed. This is certainly 

 strong proof of the fact that where only a 1-c.c. dose of virulent 

 blood is used and a larger dose of serum employed the danger is 

 practically nothing. This, of course, providing that the serum 

 used be of good quality. This point cannot be too strongly em- 

 phasized. The quality of the serum is absolutely all important 

 where the double treatment is to be given. Double treatment 

 with a poor grade of serum means that there will be a lot of funerals. 



It must not be understood by the frequent references here 

 to poor-grade serum that only commercial serums are meant. 

 It is by no means always true that serum made by commercial 

 firms is of low grade. Some of the best serum made in this country 

 is made by commercial manufacturers. Some of the most expert 

 men in the United States are employed in the manufacture of 

 hog-cholera serum for commercial firms. On the other hand, 

 the state laboratories by no means always turn out a perfect serum. 

 The salaries paid by state institutions are not large enough to 

 attract the very best grade of workers to this field. A high-grade 

 serum maker can secure more salary working for a commercial 

 firm, as a rule, than he can for a state experiment station. 



