52 Causes of Disease. 



many; vipera Redii and ammodytes in southern Europe, the dif- 

 ferent species of crotalus (or rattlesnake) in America, possessing 

 poison glands in connection with the teeth or jaws. Scorpions, 

 the females and neuters among honey bees, wasps and bumble 

 bees possess poison glands and a sting at the posterior end of the 

 abdomen ; toads and salamanders, wart-like skin glands ; hairy 

 caterpillars, many biting flies, gnats and gadflies, salivary glands. 

 There are certain species of fish, like the barbel, whose sexual 

 glands contain a poisonous fluid and whose tins are provided with 

 a poisonous substance derived from the skin glands. It is not 

 certain whether the occasional poisonous qualities of edible 

 mussels, oysters and star fish depend on transient gland secre- 

 tions (sexual seasons), upon the food of these animals, or whether 

 they arise from bacterial changes of the animal after death. 



The changes caused by poisons are partly limited to certain 

 localities, partly connected with general anatomical and physio- 

 logical changes.* 



The poisons may be arranged for classification in four groups, 

 according to their modes of action: (i) Corrosive, locally irri- 

 tative poisons; (2) Parenchymatous poisons: (3) Hccmic poisons; 

 (4) Nerve and Cardiac poisons. I\Iany do not confine their in- 

 fluence to a simple type, but Excite lesions and symptoms of mul- 

 tiple character simultaneously. 



The corrosive and locally irritative poisons {caustica, irritan- 

 tia) vary in their results with the dosage and concentration of 

 application and with the character of the tissue with which they 

 come in contact, ranging from simple hyperemia and inflammation 

 to coagulation, eschar-formation and solution of the tissues. 

 Such lesions depend upon special properties of the substances, 

 as abstraction of water from the tissues, precipitation or solution 

 of the albumens, formation of precipitates in mucus forming tis- 

 sues, solution and decomposition of urea, conversion of fats and 

 carbohydrates into acids, as well as production of a variety of 

 chemical changes in the salines of the body or other destruction of 

 the structure of the living protoplasm. Among these caustics and 

 irritants (to the skin or mucous membranes by direct contact) 

 are included the corrosive acids (sulphuric, nitric, hydrochloric, 

 oxalic, osmic, acetic, carbolic,! etc.). the caustic compounds of 

 the alkalies and alkaline earths (potassium and sodium hydrox- 



•The following is taken from the works of Samuel, Zlegler and Blrch- 

 Hlrschfeld. 



tCarbolic acid or phenol is really an alcohol. 



