184 AN EXAMINATION OF THE 



3. — Hairs and threads of various fabrics. 

 4. — Particles of sand, glass, metals, soot, and starch. 

 5. — Parts of chitinous shells of small insects. 

 6. — Bits of feathers, and the pappus bristles of composite 

 plants. 



7. — Minute, highly-refracting particles, simulating micrococcus, 

 8. — Crystals of various forms and sizes. 

 9. — Pollen-spores of many different kinds. 

 10. — Leaf-hairs. 



II. — Mycelium and spores of fungi. 

 12. — Nucleated cells, resembling leucocytes. 

 13. — Bacteria, as bacterium^ vibrio^ bacillus, and micrococcus ; 

 and under the forms of aggregation kno^vn as zooglcea, " swarms " 

 leptothrix, and toriila. 



When observed fresh, after preservation for a longer or shorter 

 time in well-stoppered glass bottles, the same moisture has 

 contained, besides many of the objects above noted : — 



I. — Living algae. 



2. — Amoeba, flagellate and ciliate infusoria. 



3.— Fungi. 



4. — Bacteria of many forms. 



Specimens collected by the vane microscope (Fig. 2) and 

 mounted in glycerine abounded in pollen, leaf-hairs, spores of 

 sphxria, epithelium, and detritus, both organic and inorganic. 



Dust, collected dry, by simple exposure of sHps and discs to 

 the air, contained sand, soot, etc., and numerous crystals, mostly 

 rods and radiating needles. 



And, finally, the discs and tubes containing collections 

 made in hospital-wards abounded in epithelium, starch-cells, 

 resembling leucocytes, and threads and hairs. 



Epithelium, as appears from the foregoing summary, is always 

 and everywhere present in the air. Considering the probability 

 of the communication of contagious exanthemata by this means, 

 the constant presence of epithelium in the air becomes a fact of 

 considerable hygienic importance. 



Particles of glass are often found upon air-slides, which do 

 not come from the air itself, but from the tube by which the drop 



