OPIUM — MORPHINE 189 



Circulatory System. There is practically no direct action on 

 the circulation, although the heart may be accelerated for a short 

 time by stimulation of the heart muscle or from the nausea pro- 

 duced. Large doses slow the heart by stimulation of the vagus, but 

 on account of the action upon the vasomotor center, blood pressure 

 does not fall. There is no effect upon the peripheral vessels except 

 those of the skin, which are dilated even by small doses. This is 

 especially so of the vessels of the skin of the head and neck in man. 

 The dilatation of the skin vessels gives a sense of warmth to the skin 

 and causes an increase in the secretion of sweat. 



Toxic doses of opium produce a rapid weak pulse and depress 

 all the functions so that the blood pressure falls; the skin becomes 

 pale, due to withdrawal of the blood to the splanchnic vessels, and on 

 account of asphyxia from depressed respirations. 



Nervous System. In mammals opium produces depression of 

 the voluntary movements and later an increase in the reflex irri- 

 tability, but the relative importance of these two stages differs in 

 the different species of animals and even in different individuals of 

 the same species. For instance, in the members of the cat family 

 and the horse, cow, sheep and pig, morphine rather seems to increase 

 movement. The animals run about the room, or malce circus move- 

 ments and are very restless. At the same time there is a depression 

 of the intelligence and of power of perception because they make no 

 effort to escape and do not avoid obstacles so carefully as normal 

 animals. Convulsions finally set in, similar to those in strychnine 

 poisoning. On the other hand, the depressant action is more pro- 

 nounced in the dog. After small or fair sized doses, these animals 

 pass into sleep, from which they can be easily wakened at first, but 

 this soon deepens so that it requires greater force to waken them. 

 After being aroused, the dog appears to sleep less soundly, and less 

 stimulation will awaken him if applied within a short time after- 

 wards. During the awakening period the animal may appear to 

 perform voluntary movements, but there is a lack of coordination, 

 partial paralysis of the hind extremities and lack of conscioiisness. 

 He is drowsy and stupid and soon sinks back into a deep sleep. The 

 sensation of pain seems to be much diminished, but not entirely so, 

 as the dog will often wake from severe sudden pain. The reflexes 

 at this time are much depressed. " After larger doses," according 

 to Cushny, " an exaggerated sensibility to external stimulation seems 

 present, for the animal starts convulsively on loud soimds and on 

 pinching, but when undisturbed lies in a profound sleep." 



The stage of strychnine like convulsions as mentioned in case of 

 the cat is not seen in the dog after morphine, although the reflex irri- 

 tability may be distinctly increased by large doses. 



From the above symptoms it would seem that the action upon 

 the central nervous system consists of a mixture of stimulation 



