202 
TENTH REPORT. 
the same conditions. But the widely differing conditions under which 
germicides must be used, makes any table of comparisons of only limited 
value. 
That there is very little relation between the germicidal and insecticidal 
values, is most graphically shown in the case of the coal tar products and 
the mercury salts; and it can readily be seen that no chemical investigation 
would have revealed the facts brought out by careful insecticidal and ger- 
micidal tests. Most important of all, is the fact that these values are so 
susceptible to conditions not easily recognized by a chemical assay and that, 
therefore, in many cases, chemical specifications are without value for desig- 
nating any efficient preparation. To many who are not familiar with the 
fact that some very important pharmacopoeial preparations admit of no 
test superior to a biological examination, this may seem a serious drawback. 
But surely no one will deliberately ignore the only satisfactory means of 
judging the values of such preparations. 
The toxic action of these various products show no greater similarity 
than that of the other properties. That the toxicity of the phenol series of 
coal tar derivatives does not increase as the members increase in germicidal 
value, has long been known. In fact, the toxicity is, in some cases, in inverse 
order to the disinfecting power. 
The value of a germicide or insecticide depends often as much on its nega- 
tive as its positive virtues; particularly, its lack of injury to the animal or 
the material with which it comes in contact. To determine toxicity of the 
various salts, alkaloids, and coal tar derivatives used in these experiments, 
the following described method was employed. 
Guinea pigs were dosed per stomach by means of a catheter passed between 
the forcibly opened jaws into the oesophagus and varying amounts of solu- 
tions of the different drugs, were injected through the catheter by means of a 
10 cc. syringe, the end of which fits into the catheter. This uniformity in 
the size of the dose — 10 cc. in each case, makes necessary a great difference 
in the dilution of the different drugs; the results may, therefore, in some 
cases, be misleading, because of death from local irritation rather than from 
absorption of the toxic substance. For that reason, no attempt was made 
to determine the toxicity of some compounds known to destroy tissue rather 
than to be strictly poisonous. 
In the table will be noticed the surprisingly high toxicity of Potassium 
Cyanide in solution and Arsenic and their very great difference in insecticidal 
value, while on the other hand will stand out the striking similarity in toxicity 
of coal tar derivatives other than Carbolic and Cresylic Acids and their wide 
variations in other respects. One peculiar effect coal tar preparations have 
is their being absorbed through the skin of cats. When a cat is dipped in 
a solution containing compounds of the phenol series, even when the head 
is not submerged, and the animal is not permitted to lick itself and so swallow 
some of the solution, death almost invariably follows, unless the animal is 
within five minutes, thoroughly washed free from all traces of the solution; 
while, when so washed, recovery has followed in every case noted. Where 
death has followed the dipping of a cat in a, carbolic dip, this has occurred 
after several days of very evident suffering with every appearance of its 
being phenol poisoning. 
