250 EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



throngli the catheter. Orfila used to introduce the drug into 

 an opening in the oesophagus, wliich he then ligatured to pre- 

 vent vomiting ; but since sul)cutaneous injection was introduced 

 this method is rarely employed. 



Ohscrvation of Effects. — After the drug has been administered, 

 we allow the animal to move freely about, but prevent frogs 

 from escaping by covering them with a large bell-jar. We then 

 see whether the animal is restless or disinclined to move; 

 whether its movements are perfectly performed or unsteady; 

 whether or not its legs seem weak and paralysed, or convulsive 

 movements or in\'oluntary twitchings be present; whether its 

 heart-beats or pulse, and respirations, are quick or slow, strong 

 or weak, regular or irregular; whether there is vomiting or 

 purging, diuresis, salivation, dryness of the mouth, flow of 

 tears, or dry conjunctiva, and whether the pupil be contracted 

 or dilated. If the animal seems asleep, we pinch it to ascertain 

 if reflex action continue after voluntary motion is gone; and if 

 respiration cease, we ascertain if the heart still continue to beat. 

 As soon as possible after death, w^e open the animal and see if 

 the heart still be beating. If it have stopped we note whether 

 its cavities are full or empty, its walls flaccid or firm, and try 

 whether it will contract or not on pinching or scratching it, or 

 on irritating it by an electric current. We observe whether the 

 veins are turgid or empty, the lungs pale or congested, the 

 stomach and intestines quiet or in active peristaltic movement, 

 the spleen large or contracted, the bladder full or empty ; and 

 the urine may be tested for sugar. 



Interpretation of Residts. — If we find in the course of these 

 experiments that voluntary motion is increased or lessened, we 

 may naturally conclude that the activity of the cerebrum is 

 increased or diminished, unless the increase of motion should 

 depend on pain, or its diminution on impairment of the motor 

 apparatus. Unsteady movements, paralysis or convulsions, 

 impaired reflex action on pinching, or stoppage of respiration 

 before the heart, point to the spinal cord, to the nerves, or to 

 the muscles; while quick or slow, strong or weak pulse, or 

 stoppage of the heart before the respiration, point to the vaso- 

 motor system or cardiac nerves ; increased or diminished secre- 



