472 Agricultural Journal of Victoria. 



ANIMAL PARASITES. 



By A. A. Brotrn., M.B., B.t>. 



No. 9. 



Intestinal Kound Worms. 



The intestinal tract of animals, man included, harbors many 

 varieties of worms. There they sojourn an indefinite period of time. 

 In some instances they long take up their abode, and in other cases 

 they brietiy tarry. Removed from the tissues of the intestines they 

 soon perish, as they are quite unable to support themselves inde- 

 pendently of the tissues of their hosts. In different regions of the 

 tract different varieties of the worms are found, some live only in the 

 stomach, some in the small, and others in the large intestine. As 

 regards size, they vary considerably. Some are only a few lines long, 

 others may measure several inches in length. The age of their hosts 

 plays some important part with respect to susceptibility to 

 infestation. Young animals are more prone to be infested than older 

 ones, whose tissues are fortified against invasion. As age advances, 

 the power of the parasite to thrive diminishes, and in older animals, 

 as a rule, few round intestinal worms are ever found. When present, 

 they may, in some animals, cause marked symptoms, and in others 

 they may produce no ill result. The embryos escape in enormous 

 numbers from the alimentary tracts of the animals that harbor the 

 adult parasites, and in damp situations, or enclosed in the bodies of 

 snails, molluscs, caterpillars, worms, &c., they undergo further 

 development. Then, after a certain time, they are found as free 

 swimming agents, and are carried by the waters over the lands, 

 where they fix themselves on to blades of grass or leaves of other 

 plants used as food by man and lower animals. It is from drinking 

 water obtained from river, or well, or reservoir supply, or from the 

 consumption of food plants, that the embryos are introduced into the 

 stomachs of human beings, as well as those of lower animals. 



Lung worms, from the functions which the invaded organs discharge, 

 always cause more or less discomfort, if they do not actually seriously 

 impair health. Intestinal worms may, in some instances, exist, and 

 give no indications of their presence, and, in other cases, may cause 

 the death of their hosts either from impairing nutrition, or from reflex 

 nervous irritation, or from peritonitis, due to their having perforated 

 the bowel. When present in large numbers, wasting may be a 

 marked sign from nutrition being perverted. The food ingested by 

 animals undergoes elaboration through the chemical action upon it of 

 the digestive juices of the stomach and intestines. When digestion 

 has proceeded far enough, the soluble products of the process are 

 absorbed by the lacteals and blood vessels. A certain amount of food 

 is daily required by all animals to build up their tissues, and repair 

 tissue-waste, maintain animal heat and force, and preserve health. 

 In the animal economy, the food that is consumed not only builds up 



