ACTION OF BELLADONNA 281 



and occasionally delirium in the lower animals. Stimulation is succeeded 

 by exhaustion and some depression, with stupor rather than coma. 



Spinal Cord. — Belladonna appears to exert a double action (stimu- 

 lant and depressant) upon the spinal cord. The medullary vasomotor 

 and respiratory centres are stimulated. Large doses cause complete loss 

 of motion and reflex action in the frog, lasting for several days, and 

 followed by reflex excitability and convulsions. Poisoning in mammals 

 is exhibited by less paralyzant action accompanied by more convulsive 

 movements. Various explanations have been offered to reconcile these 

 phenomena. The prevalent theory is, that, following complete paralysis 

 pi the spindl cord, the motor Jind sensory tracts recover before the in- 

 hibitory centres, so that normal stimuli pass through the latter unre- 

 strained and result in convulsions. 



Nerves. — The action of belladonna upon the nerve endings is ex- 

 tremely important, and represents, to a considerable degree, the thera- 

 peutic value of the drug. The peripheral motor nerve terminations, and, 

 to a less extent, their trunks, are depressed and paralyzed. This is 

 never so complete, however, but that there is some voluntary power left 

 in an animal fatally poisoned. Depression and loss of function of ,the 

 afferent nerves come on more slowly, and exist to a less degree. Bella- 

 donna, then, when applied locally or given internally, is an anodyne, but 

 is far inferior in this respect to opium; and, whereas opium acts cen- 

 trally, belladonna acts peripherally. The terminations of all secretory 

 nerves are also depressed and paralyzed by belladonna, and secretions are 

 therefore diminished. 



Secretions. — Dryness of the mouth is one of the first physiological 

 symptoms following the administration^of belladonna. This is due to 

 paralysis of the peripheral terminations of the secretory nerve (chorda 

 tympani) of the submaxillary gland, and of the secretory nerve endings 

 of the other salivary and mucous glands in connection with the mouth. 

 Another characteristic effect of belladonna consists in the production of 

 dryness of the skin, wJiich follows the action of the drug in paralyzing 

 the peripheral nervous filaments supplying the secretory cells of the 

 sudoriparous glands. In the same manner the tracheal and bronchial 

 secretions are diminished, and also the secretion of milk (anti-galacta- 

 gogue action), by depression of the terminations of the secretory nerves. 

 The drug diminishes somewhat the secretions of the intestinal tract, and 

 the secretion of gastric juice is diminished or arrested; but that of the 

 pancreatic juice and bile not at all. The HCl in the gastric juice is 

 much more reduced than the pepsin or fluid as a whole. The amount of 

 urine is sometimes increased after the ingestion of small doses of bella- 

 donna, but is considerably lessened, or suppressed, in poisoning by the 

 drug. Experiments upon man show that the urinary solids are increased : 

 urea and uric acid to a slight extent; sulphates and phosphates to a con- 

 siderable degree. 



Muscles and their Nerves. — Atropine is antispasmodic in its effect 

 upon involuntary muscle. It depresses their motor nerve endings. Vol- 

 untary muscles are not affected by any doses of atropine, although the 



Digitized by Microsoft® 



