This paper is an attempt to throw a little light on what is probably the most neglected, and yet most important aspect of Artificial Insemination, namely, the management of the bulls used for this purpose.

Evidence is becoming apparent that a number of bulls used for A.I. have been discarded or compulsorily rested because they refused service. As the number of Centres increases so will the number of bulls which fall into this category, and the problem is likely to be the greatest that A.I. has to face in the future.

It is rapidly becoming obvious that this failure of sex drive is not, as generally thought, primarily nutritional, but is in a large degree due to the lack of knowledge of the psychological process involved in the sexual act, and the consequent ill-handling of the animals during service. The knowledge available on the mental processes which take place is inconclusive and complicated, and involves androgenic and oestrogenic factors and their relationship with these processes.