642 ANNUAL. REPORT OF THE Off. Doc. 



registered animals ; or the grade may be made up of a mongrel on a 

 mongrel, so that, practically^ the law is so defective in that respect 

 that the breeder can only fall back on his own judgment. 



Now, that is in reference to the law as it now stands, but your 

 Committee was appointed more especially upon Hereditary Defects. 

 My own practice in breeding, is to keep far away from any form of 

 unsoundness that may be transmitted, but, unfortunately, there are 

 stallion owners who do not do so, and, as a Committee, we are placed 

 in an embarrassing position. We are in position between justice to 

 the breeder, and, also, not to do injustice to the stallion owner. We 

 have tried to make a very conservative report based upon investiga- 

 tions and observations. I have learned that my colleague. Dr. Mar- 

 shall, of Philadelphia, has recentl}^ delivered an address before an 

 association in New York on this subject, and, in getting a copy of 

 this address, I find he has pretty well covered this question, so I got 

 his consent to read his lecture on this occasion. No doubt, you will 

 want to ask a good many questions, and, so far as I can tell, the 

 Doctor will be very glad to answer them. I shall ask Dr. Marshall 

 to come forward and read his address on that subject. It happens to 

 strike this question very fully, entirely and sufficiently: 



HEREDITARY OR TRANSMISSIBLE DISEASES IN HORSES. 



By DR. C. J. MARSHALL. 



Certain defects in animals are known to be transmissible, while 

 others are so considered for the want of a better explanation. Tuber- 

 culosis was believed to be hereditary for centuries but the searchlight 

 of modern science has shown that this factor plays an insignificant 

 part. The future will reveal the true cause of other diseases. 



Governments and a number of states have adopted stallion regis- 

 tration laws for the purpose of improving type and soundness and to 

 assist and encourage the breeding of better horses. In most cases the 

 law attempts to prevent the use of horses that are off type or have 

 hereditary or transmissable unsoundness, or are afflicted with con- 

 tagious and infectious diseases. Very few authorities state definitely 

 what such defects are. Veterinarians often experience difficulty in 

 passing judgment upon stallions for which licenses are requested and 

 are frequently criticized for condemning or passing them as service- 

 ably sound for the stud. At horse shows and fairs similar questions 

 arise. Some may be afraid to exhibit valuable sires for fear that 

 an unknown or abnormal condition might, unjustly, be considered 

 hereditary, and thereby ruin the reputation of the horse. For these 

 reasons, veterinarians should have decided opinions in reference to 

 the most common defects and work uniformly, as much as possible, 

 in passing judgment on horses for breeding or show purposes. 



In order to collect evidence on this subject, a circular letter was sent 

 to about sixty well known breeders and the same number of veterin- 

 arians who have had experience in breeding. Their opinion was 

 asked in reference to the following defects which are commonly be- 

 lieved to be hereditary: Vicious habits, blindness, roaring, emphy- 

 sema, spavin, curb, ringbone, sidebone, navicular disease, osteoporosis. 



