686 THE POPULAR SCIENCE MONTHLY. 



opes, passes into the intestine, and, by means of its hooks and suckers, 

 attaches itself to the intestinal walls, when it begins to gi'ow with 

 great rapidity, a length of many feet being attained in a few weeks. 

 The part attached is the mother or head of the taenia, and until this 

 is dislodged the worm goes on producing segments, or more propei'ly 

 proglottides, each of which is a perfect sexual being loaded with eggs. 

 These are successively detached and escape with the evacuations, to 

 be swallowed, perhaps, by some other pig, in whose flesh a new crop of 

 cysticerci will soon develop. An egg of the Taenia solmm may be 

 swallowed by a man instead of passing into the stomach of a pig. It 

 is hatched in his stomach precisely in the same manner, and the em- 

 bryo takes up Its lodging in some inclosed cavity. Some have been 

 found in the eyeball, in the lobes of the brain, in the heart, and in the 

 muscles. Whatever symptoms its presence may give rise to, it obvi- 

 ously has no chance for further progress, having selected the wrong 

 vehicle to travel in. Man harbors not only the Tcenia solium, but an- 

 other species very similar which natui-alists have only learned to dis- 

 tinguish from it during the last few years, the Tcenia medio-canellata. 

 Its cysticercus is found in beef, and is introduced when the meat is 

 eaten in a raw or partially-cooked state. Tcenia nana and Taenia lata 

 are the names of other tapeworms inhabiting man, but both are lim- 

 ited in geographical distribution. The former is found only in Egypt, 

 and the latter is confined to Russia, Poland, and Switzei-land. 



All these internal parasites, including the Trichina spiralis, which 

 we have not space to speak of further, are introduced into the body 

 either with the food or the drink, and a simple and efiectual means of 

 avoiding them is, to thoroughly cook the food and carefully purify the 

 water. 



-- 



PROFESSOR TYNDALL'S RECENT RESEARCHES.' 



OBSERVATIONS ON THE OPTICAL DEPORTMENT OP THE ATMOSPHERE IN REF- 

 ERENCE TO THE PHENOMENA OP PUTREFACTION AND INFECTION. 



PROFESSOR TYNDALL began his paper by alluding to a for- 

 mer inquiry on the decomposition of vapors, and the formation 

 of actinic clouds, by light, whereby he was led to experiments on 

 the floating matter of the air. He referred to the experiments of 

 Schwann, Schroeder and Dusch, Schroeder himself, to those of the 

 illustrious French chemist Pasteur, to the reasoning of Lister and its 

 experimental demonstration, regarding the filtering power of the 

 lungs ; from all of which he had concluded, six years ago, that the 

 power of developing life by the air and its power of scattering light 



' Abstract of a paper read before the Royal Society, January 18, 1876. From the 

 British Medical Journal. 



