Page:Popular Science Monthly Volume 17.djvu/880

860 dairymen keep their cows tethered during the summer in "splendid clover and rye grass," and feed them in winter exclusively with clover hay, linseed-cake, and rape-cake. The milk is set in such a way that the cream shall be got off while it is still perfectly sweet, for they will not churn it if it is in any other condition. The proper temperature for churning, which is from 57° to 60°, is essential, and the churning should not be continued too long. The best butter-makers stop churning at the very moment the butter appears in the form of grains like shot. They pass off the buttermilk through a strainer, then put the butter back with water, give it a few more turns in the churn, strain again, and repeat the operation till the water runs off as clear and bright as when it is put in. Salt is added by weight, at the rate of six pounds of salt to a hundred-weight of butter, by being sprinkled over the butter after it has been spread out in layers; a few turns are given the mass with the butter-worker, and the process is complete.

Diffusion of Bacteria.—M. Miguel has learned from his investigations of bacteria and germs in the atmosphere that the number of bacteria, which is small in the winter, increases through the spring, and becomes large in the summer and fall, then diminishes again during the months of frost. The same is the case with the spores of fungi; but while the molds are abundant during moist periods, the number of aërial bacteria then becomes very small, and does not increase again till the soil has been dried, precisely when the fungoid spores are rare; so that the maxima of mold-microbes and the minima of bacteria-microbes correspond with each other, and vice versa. While in the summer and fall a thousand germs of bacteria may often be found in a cubic metre of air, in winter the number falls to four or five, and on some days the dust from two hundred litres of air is incapable of causing the infection of the most alterable liquors. Usually, in M. Miguel's laboratory, the dust of five litres is enough to cause infection, and in the sewers of Paris the particles in one litre will do it. A comparison of the number of deaths in Paris from infectious diseases with the number of bacteria present in the atmosphere showed that every increase of bacteria in the air was followed in about eight days by an increase of the deaths in question. M. Miguel further represents that he has found that the water vapor which rises from the ground, from rivers, and from masses in full putrefaction, is always micrographically pure, that gases from buried matter in the course of decomposition are always exempt from bacteria, and that even impure air sent through putrefied meat is purified under certain conditions.

The Thread-Worm of the Dog.—The cruel thread-worm (Filaria immitis) of the dog was described thirty years ago in the "Proceedings" of the Academy of Natural Sciences of Philadelphia, and has since been repeatedly noticed as infecting dogs in Europe, India, China, Japan, and this country. The heart of a dog, with the ventricles stuffed with the worms, is preserved in the Museum of the University of Pennsylvania. A specimen of the heart and part of one lung of a dog containing the worms has recently been sent to the Academy of Natural Sciences, by Mrs. Laura M. Towne, of Beaufort, South Carolina, who has also furnished a description of the symptoms shown by dogs afflicted with the parasite. She had lost several dogs, and a gentleman living on a neighboring island had lost more than thirty hunting-dogs in two or three years with the same symptoms. The most characteristic symptom appears to be a peculiar cough, which is excited by any movement, especially after sleeping, ending in a violent effort to bring something from the throat, but nothing is thrown up. When they began to run violently, the afflicted dogs would fall down and become stiff and insensible, but would in a short time get up and renew the chase. A large Newfoundland dog grew ill, exhibiting the drowsiness, lassitude, and inclination to turn round and round when he attempted to go anywhere, which marks the conduct of sick dogs, and finally became subject to spasms. He was examined after death, when one filaria was found lying at full length in the windpipe, and others were found stretched at length and crowded closely in the large artery. Upon cutting into the heart, the worms