82 LEONE LL c. STRONG 
wall. This second incision should be made a little to the right 
of the midventral line. The edge of the cut is held up slightly 
with a pair of small forceps in the left hand. Another pair of 
forceps is inserted into the opening and pushed caudad, care 
being taken to avoid touching the urinary bladder. The testis 
is easily withdrawn through the incision. By holding the 
testis with one forceps and manipulating the other pair of 
forceps freely, the testis can be severed from its normal con- 
nections. Bleeding can be prevented by pinching, before 
severing with forceps, the few cut blood vessels. The adipose 
tissue together with the sperm duct can then be pushed back 
into normal position. Care should be employed not to touch 
the alimentary canal (or any other structure in that region 
except the testis), as adhesions may result. There should be 
practically no bleeding. The inner wall of the body cavity is 
sutured by means of silk, one stitch is usually sufficient. The 
outer wall is sutured by means of two stitches. The area can 
then be moistened by a piece of absorbent cotton that has been 
dipped in warm water. The mouse is then kept warm until 
it has completely recovered from the effects of the ether. 
Spaying. The operation for removing the ovaries is somewhat 
different. The hair is first clipped from an area of about one- 
half inch square on the dorsolumbar region. The assistant 
then places the mouse dorsal side up, the right hand holding 
the hind legs stretched out at an angle of about 45°. With 
the left hand the small etherizing bottle can be manipulated. 
The mouse is kept in position by holding the ears with the 
left hand. The mouse is very easily smothered by the slightest 
pressure in the region of the neck. A single longitudinal in- 
cision (about three-eighths inch long) is then made in the mid- 
dorsal line about one-third the distance between the base of 
the tail and the neck. A pair of forceps is worked around under 
the skin near the incision, thus making the skin freely movable 
from the body wall for about a square inch. The skin is pulled 
over to one side until the incision coincides with a line drawn as 
a continuation of the outer surface of the hind leg. The point 
thus determined should be directly over the position of the 
