AERIAL SPORES. 127 
experiments with an “aeroscope,” which he invented for the pur- 
pose, was to give as his opinion that spores and ova were infinitely 
rare in the atmosphere even in places where they should be expected. 
In 1860, M. Pasteur made his appearance, and fresh light seems 
to have dawned with his début. By means of an aspirator he 
drew air through a plug of gun-cotton, and proved the existence 
of all kinds of spores in the atmosphere. Since this time, M. 
Pasteur has worked assiduously at this and collateral subjects, and 
has helped not a little to further the employment of the microscope 
in the investigation of the causes and nature of disease. 
In America, we have Dr. Salisbury’s investigation on the 
epidemic of intermittent fever which occurred in 1862 in the 
marshy valleys of the Ohio and Mississippi, in which he placed on 
record that having examined the saliva and mucus from the mouth 
and zares of the sufferers, he detected the presence of animalcules, 
diatoms, desmids, cells and filaments of algze, and spores of fungi. 
Verily one of these poor patients must have been quite a treasure 
to a working microscopist. 
Dr. Maddox, in the June number of the Monthly Microscopical 
Journal for 1870, had an admirable paper on the subject, which 
was illustrated by a drawing of the aeroscope he employed, and 
which was very similar in all points to that devised by Pouchet, but 
differed from this latter by the fact that the air current traversed 
the apparatus without the use of an aspirator as was used in 
Pouchet’s instrument. In summing up he says, “ Hitherto I found 
besides organic and mineral matters (débris) pollen grains, minute 
germs of various fungi, or protophytes, and excessively minute 
bodies, molecules, globules,” &c. Now, although Dr. Maddox in 
his paper speaks of using the ;,th and .,th objectives, yet the photo- 
graphs, by means of which the paper was illustrated, were only 
magnified 43 and 118 diameters, powers entirely insufficient to 
show those minute organisms which are supposed to be of real 
importance with regard to disease. 
Several other microscopists have worked at this subject ; it is not 
necessary to mention each one individually ; they have all in their 
turn helped to sway the balance to and fro. One finds bacteria in 
the air, and another tries immediately to disprove his statements, 
and all these quibbles have chiefly arisen from the fact that most 
microscopists who have essayed to experiment upon this most 
difficult subject have neglected those conditions which are neces- 
sary to scientific accuracy. 
The observer who has left us some permanent record of what he 
has actually seen is Dr. Cunningham, and one of his drawings we 
have reproduced as Plate VI. It represents the spores collected 
by him during 24 hours from the atmosphere of Calcutta, on the 
7th of August, 1872. 
