PARASITES OF MUSCLE 121 
interval between ingestion of trichinous meat and muscle 
infestation is ten days. On arriving at its destination, 
each larva coils itself into a spiral, and by its presence 
irritates the tissues, so that eventually fresh connective 
tissue is thrown out from that already between the 
bundles of muscle fibres, and a cyst wall is formed around 
the parasite. 
Each cyst is somewhat ovoid and pointed at the 
extremities, and in its length lies parallel with the direc- 
tion of the muscle fibres. The length of the cyst is from 
0-3 to o-8 millimetre. 
The commonest seats of infestation are : 
Pillars of diaphragm. 
Muscles of tongue and larynx. 
Shoulder. 
Intercostals. 
Psoas muscles. 
Adductors of thigh. 
DAR Y NH 
The muscles are infested to a greater extent close to 
their insertions. 
In order to discover Trichina cysts in pork, thin strips 
are cut from the pillars of the diaphragm, tongue, etc., 
in the direction of the muscle fibres. These should be 
macerated in a mixture composed of pot. chlor., 1 part, 
and acid. nitric. dil., 4 parts. The strips are then shaken 
in water, placed between two slides, and examined micro- 
scopically. The coiled-up larva is then easily visible. 
When trichinosis has been present for a long time 
calcareous or fatty degeneration sets in, and in the 
former case the cyst becomes hard, and gives a gritty feel 
to the meat. Pigment may also be deposited in the cyst. 
Calcareous and fatty deposits usually render the parasite 
harmless. 
Symptoms.—In the pig symptoms are usually absent. 
If the number of invading Trichine is large, the first 
