STEPS OF AN INVESTIGATION. 249 



is necessary; and, if it were given to a man weighing 150 lbs., 

 in order to stop the exit of corpuscles from the vessels in such 

 a disease as peritonitis, 3 or 4 drachms of the medicine would 

 require to be given within a short time. Binz's observations as 

 to the effect of quinine on the white corpuscles have been con- 

 firmed by Martin, but have been denied by Schwalbe, so that 

 further investigations on this point are very desirable. 



Action of Gases. — This is examined by putting the cells to be 

 examined on Strieker's warm stage, and bringing the gas into 

 contact with them in the manner described by him.* 



Steps of an lu'vcstigation. — The animals wliich we chiefly 

 use in experiments are frogs, rabbits, guinea-pigs, and dogs. 

 In investigating tlie action of a drug, we examine — 



1. What the symptoms are which a large dose produces. 



2. Taking the most prominent symptom, we inquire (a) On 

 what organ does the production of this symptom depend ? (b) 

 How has it been affected by the drug ? (c) Has this afi'ectiou 

 been primary or secondary ? 



3. We examine other organs which we think may have been 

 also affected. 



Adininisiration of Drugs. — To examine the general effect of 

 a drug, we weigh the animal and then give it a large dose in 

 •our first experiment, in order to get exaggerated symptoms. It 

 may be given by the mouth or by subcutaneous injection. In 

 frogs, the substance may be injected either under the skin of 

 the back or into the abdominal cavity. In rabbits, &c,, it is 

 most conveniently injected under the skin of the flank. In 

 guinea-pigs, the abdominal parietes are very thin ; and, if we 

 wish to compare experiments with different doses, care must be 

 taken not to push the point of the syringe into the abdominal 

 cavity, as the absorption will be then more rapid, and the same 

 dose produce a greater effect. If we wish to give the medicine 

 by the mouth, we either put it well back on the root of the 

 tongue and then hold the animal's jaws together till we think it 

 has swallowed it, or we put a perforated cork between its teeth, 

 push an elastic catheter through the hole in the cork down tlie 

 cesophagus into the stomach, and inject the drug in solution 



* Siric'.cr"s Uistol igt/, Sydenham Society's edition, p. 8. 



