CHAPTER III 



DERMATITIS 



Skin diseases are produced by a variety of causes, some resulting from 

 pathogenic organisms and others through the ingestion of food. On account 

 of these differences, we have two 

 classes sometimes given : parasitic 

 skin diseases and urticarial diseases. 

 Under the second class are placed 

 such eruptions as those produced by 

 buckwheat and smartweed, known 

 technically as fagopyrismus and rhus 

 venenata {dermatitis), and urticaria, 

 the latter being produced by a large 

 number of plants, especially the 

 nettles. Or there may be internal 

 causes due to innervation of vaso- 

 motors. Of the parasitic skin dis- 

 eases known under the general name 

 of dermatomycoses, we have sever- 

 al types, the co-called Tinea ton- 

 surans and the Favus organ- 

 isms, the former occurring in cattle, 

 dogs, horses, sheep, swine, and poul- 

 try. 



This term is derived 



Dermat- from two Greek words 

 omycosis. meaning skin and fun- 

 gus. The classification 

 of the fungi concerned is not at all 

 satisfactory; at present, however, 

 they are generally included in the 



groups known as Fungi Imperfecti, 

 the Mucoraceae and Ascomycetes. 



The Fungi Imperfecti include a cause of dermatitis o/ Rhus poisoning (U t S. 



large group of fungi whose life his- Dept ' AgrL) ' 



tory has not been worked out completely. The fungi of this class are form- 

 genera, such as the favus fungus. The so-called Achorion and Trichophyton 

 of various authors represent such form genera, the Oidiuni albicans being 

 another type; of these, some, perhaps, never produce any other kind of spore 

 than the one commonly seen. 



Many of these genera undoubtedly belong to the Ascomycetes, in which 

 the spores are produced in little sacs called asci, the spores being known as 

 ascospores. A kind of ringworm of the dog (Hidamella spinosa) belongs to 



Fig. 1. Poison Ivy (Rhus Toxicodendron) 



