SELECTION OF A SERIES OF OBJECTIVES. 181 
wards on gelatine, with addition of infusion of flesh, peptone, and 
sodium chloride, the micrococci have on serum of blood the form 
of a greyish pellicle on the surface, and an opaque cylinder in the 
interior of the serum. The cultures on gelatine were especially 
characteristic, and were propagated for eight generations. They 
resembled a nail with hemispherical head, and consisted of densely 
crowded micrococci, usually of elliptical form, but with no envelope. 
They were also cultivated on potato. 
Experiments were also made in inoculating the pneumonia- 
micrococci in animals, by injection into the right lung. With rabbits 
no success was obtained ; while mice always died in from 18 to 
28 hours. In the cavities of the pleura, partly in the fluid, partly 
in the lymphoid cells, were masses of micrococci, with all the 
characters of those of pneumonia, including the envelope. They 
were also found in the lungs and blood. With dogs and porpoises 
no result was obtained in some cases, while others were successful. 
Experiments were also made with mice by inhaling; when some 
only were infected. 
The size of the micrococci and development of the envelopes 
differ considerably with men and other animals. Those of mice 
were, on the average, larger than those of man ; those of porpoises 
were smaller, but with broader envelopes; those of dogs were 
scarcely larger than those of man, and the envelope comparatively 
narrow. The mode of preparation also has an influence on the size 
of the micrococci.—/. 2. AZ. SS. 
SELECTION OF AYSERIES OF OB] ECTIVES 
{EVERAL writers have published their views on this subject, 
differing (with the exception of Dr. Carpenter) more or less: 
from those put forward by Prof. Abbe in his paper on the “ Relation 
of Aperture and Power.” 
Dr. G. E. Blackham + selects ‘‘as a set of powers sufficient for 
all the work of any microscopist the following :— 
One 4 in. objective of o‘ro N.A. = 12° air angle nearly. 
One 1 in. objective of 0-26 N.A. = 30° air angle nearly. 
One 1/6 in. objective of 0°94 N.A. = 140° air angle nearly. 
One 1/8 in. objective of 1°42 N.A. 
The first two to be dry-working objectives without cover correc- 
tion, the third to be dry-working with cover correction, and the 
+ Proc. Amer. Soc. Micr., 6th Ann. Meeting, 1883, pp. 33-41, 227-31. 
