ZOOLOGY AND BOTANY, MICROSCOPY, ETC. Ill 



protoplasmic substance breaks up into the minute particles which 

 develope into bacteria ; (2) the stage of putrefaction in the narrower 

 sense, in which the substance is decomposed into certain fluid and 

 gaseous bodies, finally into ammonia, water, and carbonic acid. There 

 is therefore no contradiction between the statements that bacteria are 

 products of putrefaction, and that putrefaction is the result of 

 bacteria. It is quite possible for contagious diseases to arise inde- 

 pendently of infection. The author further describes the mode in 

 which vibrios, spirilla, cocci, bacilli, and other bacteria are formed 

 inside the cell out of its protoplasm. Their appearance is a sign of 

 the disintegration of the cell, and is accompanied by a cessation of 

 the current of the hyaloplasm. 



Hourly Variations in Aerial Bacteria— Miquel's Nutritive 

 Paper.* — Dr. P. Miquel, who for the last ten years has been carefully 

 studying aerial bacteria, has published some very striking results 

 showing that the number of bacteria vary from hour to hour, and have 

 approximatively regular maxima and minima in the course of the 

 entire day. At 8 a.m., the number of bacteria is high and decreases 

 up to midday. From midday to 1 p.m., there is a remarkable 

 minimum and then a gradual increase. At 8 p.m., the air is strongly 

 infected. From 10 to 11 p.m., the air is very impure, the impurity 

 decreasing from 1 to 3 a.m., to be followed by a considerable morning 

 increase in the number of aerial microbes. Two out of six experi- 

 ments were disttirbed by rain, but the remaining four gave identical 

 results. Supposing the number to be 50 per c.cm. of air at midday, 

 the rise may be up to 1000 in the same quantity of air at 8 p.m. 



These daily fluctuations Dr. Miquel finds true for all seasons. 

 The different directions of the wind do not modify them, provided 

 the direction remains constant, and the speed of the wind causes no 

 sensible variation on these periodicities. The law may be stated 

 thus. The air is less pure morning and evening than at midday, or 

 the air is more impure at the rising and setting of the sun than 

 when it is near the zenith and nadir. The law for these variations 

 remains to be discovered. Dr. Miquel suggests that oblique currents 

 determined at the surface of the earth through its daily heating and 

 cooling may go far to solve the difficulty. The winds that graze 

 the ground are supposed to charge themselves with more germs than 

 those which arrive at the place of the experiment at the incidence of 

 80° to 70°. 



To determine these variations more correctly, led to the con- 

 struction of a registering ajjparatus for houidy variations, and to the 

 employment of a neutralized sterilized nutritive paper 10 cm. wide 

 by 60 cm. long which is wound round a drum driven by clockwork, 

 all being placed under a large glass shade with certain precautions. 

 The air is aspirated upon the paper through a narrow slit in the side 

 of the shade, to the top of which the tube of the aspirator is fixed, 

 thus saving the enormous trouble of drawing air consecutively into 

 600 or 800 sterilized flasks containing neutral broth. The drum of 

 ebonite makes one turn in twenty-four hours, this with its band of 



* La Semaine Medicale, 6th Nov., 1884. 



