PRINCIPLES OF LIVESTOCK BREEDING. 13 
been treated, was likewise feeble. Prof. L. J. Cole, of the University 
of Wisconsin, has obtained similar results on treating male rabbits 
with lead. Several other experiments have been made along this 
general line, some of which confirm the preceding results, while 
others were negative. It seems clear that it is possible to injure the 
hereditary qualities of the reproductive cells by means of substances 
in the blood, but that it is not at all easy to do so. 
INHERITANCE OF ACQUIRED CHARACTERISTICS. 
The question whether a specific change in the sire, due to training, 
care, or accident, can be transmitted to the young, is quite inde- 
pendent of the question whether a general loss of vigor can be pro- 
duced in any such way. As we have seen, the latter can be accom- 
plished through the use of poisons, such as alcohol or lead, and the 
possibility exists that extreme malnutrition may sometimes have 
such an effect. The mechanism is at least easy to understand. 
This is not the case with a specific characteristic. 
There is a strong negative evidence in certain cases. Weismann 
cut off the tails of mice for 19 generations without causing any 
modification of the young. Docking the tail of sheep and many 
similar practices have no hereditary effect. Thus it can be stated 
very positively that the effects of mutilation or accidental injuries 
are not inherited. 
With regard to the functional characteristics in which livestock 
breeders are most interested, the evidence is not so clear cut but is 
still negative when of a critical character. F. R. Marshall has shown 
that the average age of the sires of 2.10 trotters was practically the 
same as that for all Standardbred horses of the same period, indicating 
that longer training has no effect on the speed of the progeny. F. S. 
Putney made an analysis of the records of the Jersey herd at the 
Missouri Agricultural College and found no relation between age of 
dam and butterf at record of the daughter. 
The failure of acquired characteristics to be inherited does not 
mean, of course, that proper care and feeding of livestock can be 
neglected, even from the standpoint of breeding. It is only by testing 
the speed of his race horses, the butterfat record of his dairy cows, 
or the fattening capacity of meat animals that the breeder can deter- 
mine which are likely to transmit the best heredity and so separate 
the desirable breeding stock from the culls. Moreover, in such a case 
as the development of an unsoundness in a horse, due apparently to 
an accident, there should be much hesitation before breeding. The 
development of the unsoundness is likely to indicate a hereditary 
weakness, and such horses will be found in general to have sired 
unsatisfactor}^ colts before the accident and will continue to do so 
thereafter. 
