DE. E. KLEIN ON THE SMALLPOX OE SHEEP. 
223 
form the groups, viz. small spheres not markedly larger than the highly refractive ones, 
the centre of which is different from the peripheral part, the former being transparent, 
the latter a highly refractive substance : then there are others whose central transparent 
part is greater, the highly refractive substance representing only an envelope, generally 
possessing at one spot a thickening ; these spheres are markedly larger than the solid 
granules, and smaller than the perfectly transparent spheres above mentioned : further, 
there are others that are still larger, and whose highly refractive substance is reduced to 
a very thin envelope, possessing at the same time at one point a minute granule. It is 
quite evident that these are transitional stages. 
If the preparation is kept for twenty-four hours in the incubator at a temperature of 
about 38° C., the number of transitional spheres is immense ; they are either isolated or 
form couples with each other or with one solid or one perfectly transparent sphere. 
( d ) Very bright shining highly refractive spheres, which are not only of a character- 
istic brightness and somewhat greenish in colour, but which appear at least of twice 
the size of the first-mentioned dark granules. They are found to form small groups, 
chiefly composed of couples, which resemble rod-like structures with terminal swellings, 
the more so as there is a more or less distinct connecting substance between the two 
joints. Some of these couples appear to be surrounded by a narrow clear zone limited 
by a thin membrane. There are also isolated bodies of this kind to be seen, which 
appear to be in the act of division, viz. a somewhat elongated sphere of the same bright 
substance showing a slight constriction in the centre. 
If the preparation has been kept for twenty-four hours in the incubator, the above- 
mentioned pale transparent masses containing irregularly distributed granules are seen 
to undergo some remarkable changes. They become more or less distinctly fibrillar, in 
such a manner that they appear to consist of a feltwork of very delicate branched fila- 
ments, in or on which the granules are now found. Plate 29. fig. 2 gives a very accu- 
rate representation of them. Under a very high power (such as an immersion-lens) we 
see that these masses consist of spherical bodies, granules of different sizes arranged in 
rows : the members of each row are imbedded in, or, rather, connected by, a pale trans- 
parent substance ; hence the appearance of minute granular fibrils. In some places the 
granules seem to lie only alongside the fibrils. Still later (forty-eight hours) the net- 
work of fibrils is very distinct, especially because the large masses, after having enlarged 
considerably, are seen to break up into smaller masses, in which it is easier to trace the 
individual fibrils. 
The granules have increased considerably in size ; and now it is very easy to recognize 
that they correspond completely to the spheres above mentioned as (l) and (c ) ; that is 
to say, that the highly refractive spheres (the granules) become gradually transformed 
into transparent spheres bordered by a delicate membrane, and that all these spheres 
bud on, and become separated from, the filamentous matrix. 
The longer a period the preparation is subjected to the constant temperature, the 
more numerous highly refractive and transparent spheres originate from that matrix. 
2 h 2 
