Fig. 308.—Catheter for cows.
PASSAGE OF THE CATHETER IN THE COW.
It sometimes becomes necessary to examine the bladder of the cow.
There is an obstacle, however, to the introduction of the sound into the urethral canal. The meatus urinarius is covered by a little valve which springs from the lower wall and forms behind the real opening of the urethra a cul-de-sac, into which the point of the catheter is apt to pass. The instrument usually employed is of gutta-percha, glass, or, better still, of metal, as more easily sterilised (Fig. 308). It is held like a pen, and is directed along the floor of the vagina as far as the opening of the meatus, being guided by the index finger of the left hand, which has previously been introduced. The point being very slightly depressed, it enters the cul-de-sac. It is then only necessary to reverse the movement, that is to say, raise the point, whilst gently pressing forward; a slight resistance is felt and the sound enters the bladder. If necessary the little valve may be held down by gently pressing on it with the point of the left index finger.
It is sometimes an advantage to expose the seat of operation. In such cases the lips of the vulva and the walls of the vagina may be separated by retractors or by the use of a speculum.
CASTRATION.
Castration is performed for the purpose of removing the reproductive power, either by obliterating the testicle or ovary or by suppressing their functions.
In ruminants, the testicles are elongated and placed in a vertical position, the upper portion of the scrotum presenting a constriction and the whole scrotal mass resembling in shape a cone with its base downwards.