PARENCHYMATOUS AND INTERSTITIAL INJECTIONS. 
31 
medicines employed, in this or a similar way, for aneurism, by 
injecting coagulable material into the aneurismal sac, no doubt 
with some very favorable results. However, I scarcely think for 
this latter pathological condition the injection could be regarded 
as interstitial; nevertheless, it is deep. 
The most frequent cases met with where this method of local 
medication could be employed is, in treatment of sluggish 
tumors and deep-seated abscesses. The advantages of proper 
agents injected into the intimate structures of the enlargement, 
over the external applications hitherto employed, are considerable. 
A case of chronic abscess under the levator humeri muscle at the 
base of the neck can be treated in a comparatively short space of 
time by the introduction of 3 ij cantharidal collodion repeated 
about every third day until pus is brought to the surface, lest a 
violent reaction supervenes, characterized by an enormous swell¬ 
ing, which must be dispersed by warm bathings and appropriate 
lotions before another injection can be made. The changes the 
tumor undergoes are marked and manifested. The enlargement 
itself is considerably aggravated. The adjacent structures be¬ 
come swollen. In twenty-four to forty-eight hours the swelling 
sinks downwards towards the sternum and into the anterior extrem¬ 
ity. The tumor proper is again circumscribed, probably larger, 
and of a more inflammatory type. In some cases the presence of 
pus might be detected by the fluctuation at some prominent 
spot. Very often, though not necessary, this at the entrance of 
the needle, though this puncture is usually entirely closed. If 
pus is detected, evacuation would next be in order; if not, 
another injection is indicated, not regarding the point where the 
original puncture was made. The operator should continue on 
with the injection about every third or fourth day, until indica¬ 
tions of pus are apparent, when it should be eliminated by a bold 
incision. This usually reveals the presence of two cavities; one, 
superficial, immediately beneath the skin; the other, deep, behind 
a fleshy, sometimes cartilaginous partition, separating the two 
cavities. This septum in turn must be pierced with a probe- 
pointed bistoury or the index finger, to furnish an exit for the 
deep-seated pus—that being the important cavity. Usually the 
