FALSE PAKASITES. 105 



pillar of Aglossa pinguinalis, which lives in old fat or butter, aud is 

 therefore frequently found in the kitchen and cellar with fat 

 articles of food. (This caterpillar was found by Rolaiider and 

 Linne in the faeces or vomitings, and regarded by the latter as 

 very dangerous in the human intestine. If they are soon 

 thrown up, they are either still alive, or retain their form ; but if 

 this take place later they must bear more or less distinct traces 

 of digestion about them. In the fseces they can hardly be found 

 again, or only in cases of very imperfect digestion, and with 

 violent diarrhoea to drive them very rapidly through the intes- 

 tines. The same applies to the Gordius aquations, which, how- 

 ever, from the hardness of its epidermis, may perhaps long resist, 

 if not death, at least digestion. It might probably reach the 

 stomach by the use of worm-eaten fruit. We know nothing of 

 species of Mermis accidentally getting into the stomach with 

 water, &c.) 



In southern countries leeches (Hamopis vorax) are readily 

 swallowed with water, and these are said to be able to live some 

 time in the human body, causing violent internal haemorrhages. 

 This is mentioned by Larrey, and it was also experienced at the 

 siege of Mahon. 



Lastly it may be stated, that hairs, fibres, and undigested 

 flesh, passed with the fseces, have been described as parasites 

 of man. The careful practitioner will be easily able to avoid mis- 

 takes. 



The hair of the processionary caterpillar (Bombyx proces- 

 sionea), which forms on oaks a bag-shaped cocoon often as large 

 as a man's head, is very dangerous to man. 



Nicolai's researches and observations (' Die Wandert oder 

 Processions-Raupe/ Berlin, 1833) have proved that the caterpillar 

 usually appears during the middle of May, at first to the num- 

 ber of from ten to twelve, on the bark of the oak, from whence it 

 wanders to the first buds and twigs of the oak. Each single 

 caterpillar is from 3 4"' in length, and of the colour of the 

 bark of the oak. They have long stiff black and white hairs or 

 bristles, and a black stripe on the back. This little band of 

 from ten to twelve caterpillars (probably relatives) keeps together 

 on a twig, and eats during night and day. They grow rapidly, 

 learn to move more quickly, upwards of 100 and more uniting 

 and forming a wandering colony in order to attack larger 

 branches. They wander thus from twig to twig, casting their 



