22 
Proceedings of the Royal Irish Academy. 
material which (being lately part of the patient's body) conveys the 
patient's malady to another person, in peculiar states of the system. 
With respect to figs. 8, 9, 10, 11, 12, 13, and 14, they were dis- 
covered in the atmosphere of the Theatre lioyal ; fig. 8 represents 
merely inchoate dust and granules ; fig. 9 is more interesting, for here 
we have a group of salivary corpuscles, and some fragments of epithelial 
scales, the group being formed by a drop of the condensed moisture of 
the breathing crowd. Figs. 10, 11, 12, 13 are fragments of epithelium 
drifting about by themselves; and amongst the granules of fig. 14 
are likewise a few such fragments, whilst there are also some salivary 
corpuscles. 
Where persons are compelled to breathe the excreted matter of 
others, conditions of disease become correlated with the frequency of 
this matter, but most especially with its liability to decay or putrefy. 
YI. FUETHEE, ReSEAECHES GIST THE AtMOSPHEEE. By GeOEGE SiGEESON, 
M. D., Ch. M., F. L. S. (Plates YIII., IX., & X.) 
[Read June 13, 1870.] 
Since my first paper upon this subject I have had the opportunity of 
reading Professor Tyndall's Lecture on Dust and Disease." As he 
lectured on Saturday, and I on the Monday following, I had not 
observed any report of it in our Dublin Papers, and was somewhat at 
a loss, until I read it, to understand why Dr. Stokes should have con- 
sidered me committed to the ''germ theory" of disease. Professor Tyn- 
dall appears to regard it with favour ; but I was not then the advocate, 
nor am I now, of a theory of '' germs" (as hereafter defined), whilst 
maintaining that mineral, vegetal, and animal matter may produce, or 
communicate ''disease." 
Let me make one remark. There was some question raised con- 
cerning my statement, that I discovered in the air of crowds and cities 
muriate of ammonia in combination with mucus. Since then Dr. Angus 
Smith has found, by chemical examination, what he calls albuminoid 
ammonia, or ammonia of albumen, present in the air of Manchester. 
This I regard as a corroboration of my statement. In the June of last 
year, when getting some photomicrograms taken, one of my chief rea- 
sons for resorting to photography was in order to have a faithful por- 
traiture of the exquisite arborescent crystallization-forms of the am- 
monia muriate. Professor Tyndall, in writing to me, observed : "It 
is to be hoped that through the researches of Dr. Angus Smith, your- 
self, and others, some definite knowledge will be arrived at regarding 
those particles, germs, and otherwise, which my experiments merely 
reveal en massed 
There was no better means of attaining a correct knowledge (it 
seemed to me) of what is usually and what is occasionally present in 
