214 VENOMOUS ANIMALS : PROTOZOA TO ARTHROPODA 



whether the cramps and convulsions are really due to action of the 

 poison upon the nerve cells, or merely to the altered blood con- 

 ditions, has not been decided. 



The reader is particularly asked to compare these actions on the 

 nervous system (neurotoxin ?), on the mucosa of the stomach, on 

 the capillary wall, on the blood and red cells, with the venoms of 

 the scorpion and of the snakes, which they strongly resemble. 



Acquired immunity can be produced in animals by injections of 

 non-lethal quantities of venom. 



Minimum Lethal Dose.— The minimum lethal dose for cats is 

 0-20 to 0*35 milligramme of the dry venom per kilogramme of the 

 body-weight. Dogs are less sensitive, and hedgehogs still less, 

 while frogs require fifty times the quantity of poison which will 

 affect warm-blooded animals. 



Effects of the Venom.— In general, the symptoms of spider-bite 

 rather resemble those of the scorpion, and are divisible into (i) local, 

 (2) general. Local inflammation is generally present, but may be 

 absent, and severe pain is felt at the site of the wound. The general 

 symptoms are those of collapse coming on gradually, with some- 

 times convulsions, or rarely a typhoidal condition ensues, which may 

 remain for weeks. Many other symptoms may also be noted, such 

 as nausea, rigors, cold sweats, dyspnoea, fever, delirium, paralysis, 

 and coma terminating in death. Inflammation of the stomach and 

 intestines, coagulation of the blood, and local haemorrhages and 

 oedema, are the principal features of a post-mortem examination. 

 The symptoms of the bites of the different spiders will now be 

 briefly described. 



Bite of Latrodectus mactans. — The symptoms of this bite are local 

 pain, which does not appear till some little time after the bite, but 

 becomes agonizing, and may last for a couple of days. In addition, 

 tetanoid symptoms may set in, but usually end in recovery in 

 about ten days. 



Bite of Latrodectus scelio. — This is the katipo spider of New 

 Zealand. The symptoms begin in about thirty minutes with the 

 formation of a white vesicle surrounded by a red halo, and severe 

 pain at the site of the bite. The general symptoms include, first, 

 stiffness of the muscles about the mouth and jaw, so that it is 

 difficult to open the mouth or to speak, and impossible to swallow. 

 The pulse becomes very slow (12 to 14 to the minute), and there 

 is extreme pallor of the face and body, with coldness of the ex- 

 tremities, which are quite flaccid. Respiration becomes slower and 

 slower, and death may take place at this stage, or an illness lasting 

 about six weeks, and somewhat resembling typhoid, may ensue, 

 which may end either in death or recovery. 



Bite of Theridium lugubre. — This bite is characterized by smart- 

 ing pains, no redness or swelling, cold sweats, restlessness, dizziness, 

 mental anxiety, depression, vomiting, cyanosis, convulsions, status 

 typhosus, and, unless improvement sets in, death in three days. 



Bite of Theraphosa avicularia.- — ^The Theraphosae come under the 



