2o6 VENOMOUS ANIMALS : PROTOZOA TO ARTHROPODA 



discussion as to whether it produces a toxin or not. The experi- 

 ments of Whipple and Preti seem to establish the presence of a 

 haemolytic principle in the alimentary canal of the worm, and those 

 of Loeb and Smith of a principle inhibiting the coagulation of the 

 blood and secreted by the cephalic glands, but these substances 

 appear to be of importance to the worm for the purposes of digestion, 

 and not to be of sufficient strength to act upon the host. According 

 to Alessandrini, however, the cephalic glands secrete a true toxin. 

 The evidence which has been gathered together points also to the 

 possibility of the toxicity of the ankylostomes being partly due to 

 the absorption of bacteria or their products into the circulation of 

 the host through lesions in the intestinal mucosae caused by the 

 bites of the worms. 



ARTHROPODA. 



The Phylum Arthropoda includes a number of types, which are 

 characterized by their capability of stinging. The forms which 

 we are about to describe occur in Class IIL, Arachnida, Class V., 

 Chilopoda, and Class VL, Hexapoda, of the classification given in 

 Chapter XXVIIL 



Class IIL The Arachnida. 



As the definition and classification of this class is given in 

 Chapter XXVIIL, we have only to consider the recognition of 

 the three orders with which we are concerned here : — 



I. Abdomen segmented — 



Tail stout and armed at the end with a sting. (Scor- 

 pionidea.) 



II. Abdomen unsegmented — • 



{a) Abdomen connected with the cephalothorax by a 



short narrow stalk. (Aranea.) 

 (&) Abdomen fused with the cephalothorax. (Acarina.) 



I. Scorpionidea. 



Scorpions abound in the tropics, where they grow to a large size, 

 and are much feared because of the poisonous properties of their 

 sting. The method of striking is to bring the tail forward over the 

 body of the scorpion, so that the curved spine on the last segment 

 (telson) of the tail penetrates into the skin and inflicts the wound. 

 On either side of this curved barb is an opening through which the 

 duct from a poison gland discharges the venom. 



It is probable that the poison of different kinds of scorpions 

 differ qualitatively and quantitatively, but on this subject little is 

 known. Certainly the sting of the small European scorpion 

 (Euscorpius europceus) has but slight action, causing only local pain, 

 redness, and swelling, while the larger one of South Europe {Buthus 

 occitanus) causes severe pain and phlegmonous swelling of the whole 

 extremity, and such remote symptoms as vomiting, faintness, 

 tremors, and cramps in muscles, while the larger tropical species 



