156 THE VENOMS OF CERTAIN THANATOPHIDE^E. 



results indicate that the profound primary fall of arterial pressure is chiefly due to 

 depression of the vaso-motor centres and is in part cardiac, that the subsequent 

 recovery is capillary, while the final fall is cardiac. The initial fall does not con- 

 tinue, because the constriction of the capillaries is, for a time at least, capable of 

 compensating the depressed action of the central organ of circulation. 



14. The respirations are primarily increased and secondarily diminished. Here 

 again we have two antagonistic factors at work together, one tending to increase 

 and the other to diminish the rate. The former is an irritation of the peripheries 

 of the vagi nerves and the latter a depression of the respiratory centres ; whether we 

 have an increase followed by a decrease or a decrease from the first will depend 

 upon the relative intensity of the action of the venom on these two parts. When 

 the action of the venom is sufficient to profoundly depress the centres the excitation 

 of the peripheries may prove futile. 



15. Death in venom-poisoning may occur through paralysis of the respiratory 

 centres, paralysis of the heart, hemorrhages in the medulla, or possibly through the 

 inability of the profoundly altered red corpuscles to perform their functions. There 

 can be no question, however, that the respiratory centres are the parts of the system 

 most vulnerable to venom, and that death is commonly due to their paralysis. 



A general survey of the chief physiological actions of venoms leads us to believe 

 that the most important effects are upon the respiratory and circulatory appara- 

 tuses, and that in the production of these results antagonistic factors are at 

 work so that we sometimes have observations which seem directly contradictory. 

 When it is remembered that there are two classes of poisons in venoms, that each 

 class possesses certain distinguishing physical, chemical, and physiological differ- 

 ences, although closely related, it is easy to conceive of the cause of the existence 

 of antagonistic actions and the necessarily varying results. 



A comparative study of the actions of the globulins and peptones indicates that 

 the (jlobulins produce swelling and blackening of the parts by infiltration of incoagu- 

 lable blood ; they are the more potent in producing ecchymoses, in destroying the 

 coagulability of the blood, in modifying the red-corpuscles, and in the production 

 of molecular changes in the capillary walls ; their action on the accelerator centres of 

 the heart is more notable than that of the peptone, hence they are more active in 

 causing the increased pulse-rate ; they exert, too, a more marked action on the vaso- 

 motor centres in producing the primary fall of pressure and are the greater depres- 

 sants of the heart ; they also act more powerfully upon the respiratory centres to 

 paralyze them. The peptones are more active in the production of oedema, in the 

 breaking down of the tissues, in the production of putrefaction and sloughing ; they 

 have little power to produce ecchymoses, to prevent coagulation or modify the cap- 

 illary walls or the blood-corpuscles ; they have less tendency to accelerate the pulse ; 

 they tend to increase the blood-pressure by irritating the capillaries, and are the prin- 

 cipal factor in exciting the peripheries of the vagi nerves in the production of the 

 increased respiration-rate. 



A knowledge of these peculiarities in the actions of globulins and peptones coupled 

 with the fact that the two classes exist in different proportions in the various 

 species of venoms is of great importance in explaining the diverse pathological 



