GUIDES IN PUNCTURING THE BOWEL. 
B17 
is only caused by the introduction of infective materials into the peri¬ 
toneal sac. It therefore becomes the chief task of the operator to prevent 
such infection ; but though it is easy to guard against soiling from without, 
it is impossible to prevent it from within, i.e., from the bowel itself, at the 
moment of withdrawal of the trochaic To minimise risk, the instiument 
must be of small calibre, as small, indeed, as will allow of fiee dischaige 
of gas. Friedberger’s model has met with wide approval (fig. 142). Canulse 
with side openings are to be avoided on account of their 
favouring infection of the peritoneal sac. 
As, however, puncture is never without danger, it is 
only justified by such pressing necessity as dyspnoea 
threatening life. 
In the horse a large portion of the colon is not directly 
in contact with the abdominal wall, but is covered by 
coils of small intestine, and is, therefore, not easily 
reached in the erect posture ; though, as animals thus 
suffering soon die of suffocation when lying, punctuie of 
the bowel is usually only undertaken in the upright 
position. It must also be remembered that the lower 
lying portions of the colon usually contain firm masses 
of food, while the gases collect in the upper parts, 
whence their discharge, by means of the trochar, is both 
easier and less dangerous. For these reasons, the seat 
of operation should be in the caecum, as its base is fixed 
at the height of the external angle of the right ilium, 
and can be found with certainty with the trochar. The 
field of operation, which is fairly extensive, is triangular 
in form, bounded above by the transverse processes of 
the lumbar vertebrae, in front by the posterior edge 
of the last rib, and below by a line drawn fr6m the 
middle of the last rib. The point to select is that which 
projects most prominently, and returns a tympanitic 
sound on percussion, but should these signs foi any 
reason be wanting, or appear more distinctly at another spot, the latter 
may be selected without disadvantage. The important matter is to 
alight on a fold of bowel filled with gas ; the larger this is the better. 
The chief difficulty lies in observing antisepsis, and, therefore, both the 
trochar and skin round the point of puncture must first be carefully 
disinfected, provided there is time. The instrument should be boiled foi 
five to ten minutes in water or soda solution, the hair shaved oft with a 
razor, the skin washed with soap and rinsed with a disinfectant (such as 
sublimate solution). If possible the field of operation should be washed 
with aether or spirit preparatory to washing with the disinfectant. 
Fig. 142.— 
Friedberger’s in¬ 
testinal trochar 
for horses. 
