18(5 



traced down to the affected part the parasites will be found in thread- 

 like bunches, completely filling the tubes. 



The symptoms of lung- worm disease in sheep can not well be diag- 

 nosed in living animals unless the disease is far advanced, and then 

 only in the severer cases. Sheep affected with either disease generally 

 have pale, bloodless mucous membranes, harsh, dry hair, a dejected 

 look, more or less difficulty in breathing, and often a deep cough. Tlie 

 bloodless condition of the sheep could arise from other parasitic 

 troubles, but the disturbance of respiration should lead one to suspect 

 lung parasites. 



Consumption or tuberculosis is apparently a rare disease in sheep, 

 and is not liable to be confused with this disease, which can always be 

 diagnosed by finding the parasite. Lung-worm disease differs from 

 acute bronchitis jor pneumonia in being of slow development, and is less 

 severe in its symptoms. Worm diseases consume weeks in develop- 

 ment, while acute diseases are begun and finished in a few days. 



THE HAIR LUNG WORM-VERMINOUS PNEUMONIA. 

 Steongylus ovis pulmonalis, Diesing. 



Plates XXIX, XXX, XXXI, XXXII, XXXIII. 



DesoHpUon.—Msile, 16"""; female, a5'""' ; width, male, 0.5""" ; female, 0.17""". Cap- 

 illary integument of worm very transparent, the cavity of the body appearing as a 

 dark line. Head not winged ; four papillas ; mouth naked. Male, bursa pointed, 

 compressed, terminal; costie (apparently) seven; one posterior; twice-notched; two 

 pair lateral, onepair anterior ; spicula symmetrical, spatulate, curved; 0.15""" long, 

 divided into two nearly equal parts; the anterior consisting of a cylindrical chitinous 

 skeleton with a membraneous expansion, the posterior of a transversely ribbed skele- 

 ton, margined by a thin broad curved membrane, thetwospicula forming a partially 

 closed tube. Female oviparous, with two uteri and ovaries. The former empty into 

 a vagina at 0.8"^" from vnlva. Vulva 0.1™™ from anus. Anus 0.08™™ from tip of 

 tail. Tail euds in a blunt point. Eggs in uteri 0.1™™ long, 0.04™™ wide. The eggs 

 segment after being laid. Embryo provided with a very sharp-pointed tail. 



Life history. — The young of the hair-lung worms escape from the lungs 

 of infected sheep and become scattered over the pastures, yards, and 

 other places frequented by these animals. They are then taken with 

 the food or drink and in some way arrive in the lungs of the sheep. 

 Arriving at the extreme ends of the bronchial tubes, they break down 

 some of the tissues and become encysted. In the cyst they grow to 

 adult size and take on .sexual characteristics. Escaping from the cysts 

 they make their way into the small air-tubes (bronchioles and bronehi), 

 where the sexes mate and reproduce. The eggs are then laid in sur- 

 rounding cavities and hatched into young worms, which make their way 

 into the neighboring air-chambers (infundibula). Afterwards some of 

 these worms may be coughed out of the lungs onto the pastures and in- 

 fect other sheep. 



In their life history there are but one or two points about which there 

 can be any question. Many learned helminthologists believe that the 



