' Cave. 
JANUARY 11, 1884.| 
plates, the following method is suggested by Laker. 
A drop of preservative liquid is placed on the slide, 
and a drop of blood on the cover-slip, and the slip 
laid quickly on the slide, so that the two drops come 
in contact. As many as possible of the red corpuscles 
are then drained off by means of a piece of filter- 
paper applied to the slip on the side opposite to the 
drop of preservative liquid; or the two drops may be 
placed on the slide, and the cover-slip laid on from 
the side of the preservative liquid. The one precau- 
tion which it is necessary to observe is to lose as little 
time as possible in transferring the blood to the pre- 
servative liquid. 
Obtained in this way, the blood-plates of the mam- 
mal are small, non-nucleated, discoid bodies from 
one-fourth to one-half the size of the red corpuscles. 
Hayem states that they are bi-concave, like the red 
corpuscles, and that many of them have a slight 
greenish or yellowish color due to the presence of 
haemoglobin. Bizzozero, on the other hand, main- 
tains that they are perfectly colorless and not bi-con- 
Mayet supports Hayem’s statement with 
regard to the presence of haemoglobin in some, at 
least, of the blood-plates; while Laker thinks that the 
pale greenish hue possessed by them is owing to a 
reflection of light from the upper surface. The same 
tint may be observed in white corpuscles; and, further- 
more, when the blood-plates are collected in masses, 
this color does not become more distinct. Laker con- 
firms Hayem’s statement that the plates are bi-con- 
caye, and says that he has often obtained from them 
the well-known optical phenomenon shown by the red 
corpuselés. The blood-plates occur in considerable 
numbers. According to Hayem, they are forty times 
more numerous than the white corpuscles, and twenty 
times less numerous than the red corpuscles. Stain- 
ing-reagents have but little action upon them. Water 
causes most of them to disappear, though some indi- 
vidual plates may resist its action for a long time. 
Dilute solutions of acetic acid or caustic alkali quickly 
destroy them, while a 35% solution of caustic potash 
is without any marked action. Laker states, that, in 
their general behavior towards reagents, they resem- 
ble most the nucleus of the white corpuscle. With 
regard to their origin, nothing is known. That they 
are not simply remnants of broken down white cor- 
puscles is evident, in the first place, from the typical 
form they possess, and, in the second place, from 
the difference in chemical composition between the 
two, as shown by reagents. Bizzozero has proved 
conclusively that they are not pathological forma- 
tions arising after the blood has been shed, since he 
has seen and studied them inthe mesenteric blood- 
vessels of living animals. 
Hayem believes that the blood-plates are finally 
transformed into red corpuscles. His reasons for 
this belief are as follows: 1. They possess a similar 
form; 2. They have a similar chemical composition, 
both containing haemoglobin; 3. The appearance of 
many intermediate forms between the typical blood- 
plate and the ordinary red corpuscle, especially in 
certain pathological conditions — after a severe hem- 
orrhage, for instance. Under these conditions, Hay- 
SCIENCE. 47 
em states that the plates become more abundant, 
and gradually return to their normal proportion as 
the number of red corpuscles increases, In the main, 
these statements are confirmed by Mayet; but, as we 
have said, the similarity in form, and the presence 
of haemoglobin, are denied by others, especially Biz- 
zozero; and neither Bizzozero nor Laker was able to 
detect any intermediate forms between the blood- 
plates and the red corpuscles. Perhaps the most 
interesting result that has come out of the study of 
these elements is the knowledge of the important 
part they take in the coagulation of blood. This 
property has been thoroughly investigated by Bizzo- 
zero. His conclusions may be briefly stated as fol- 
lows. Liquids which have a tendency to prevent 
coagulation also preserve the blood-plates more or 
less completely from destruction. Experiments made 
upon blood kept within the living blood-vessel show 
that as long as the blood remains uncoagulated the 
blood-plates are unchanged, while the rapid coagu- 
lation of portions of ,the blood removed from the ves- 
sel is always preceded by a destruction of the plates 
and the formation from them of granular masses. 
When a drop of blood is whipped with small threads 
for about fifty seconds, the threads withdrawn, 
washed gently in .75 % sodium-chloride solution, and 
then examined under a microscope in the methylated 
soda solution, they are seen to be covered with a 
layer of plates, together with some white corpuscles. 
If the whipping is continued longer, the plates are 
converted into a granular mass, and covered witha 
layer of fibrine. If this process is reversed, and a 
slow stream of blood is allowed to pass over a thread 
watched under the microscope, the different stages 
of the process can be observed, —the deposition of 
the plates, their fusion into a granular mass, and the 
subsequent formation of fibrine. When one of these 
threads, to which the blood-plates and a few red and 
white corpuscles are adhering, is added to a liquid 
containing the two fibrine factors, but not fibrine 
ferment, coagulation takes place. That this coagula- 
tion is not owing to the thread or to the red corpus- 
cles is easily demonstrated: it must result from the 
addition of either the white corpuscles or the blood- 
plates. When, however, bits of tissues rich in leuco- 
cytes — such as the spleen, lymph-glands, medulla of 
bone — are added to the above liquid, no coagulation 
at all, or else a very imperfect coagulation, follows. 
The inference, then, is, that the coagulation in the 
first case results from the addition of the blood-plates. 
In his latest communication, Bizzozero states, that if 
to afew drops of peptonized plasma, which coagu- 
lates very slowly, some water or carbon dioxide is 
added, and the preparation is examined under the 
microscope, the blood-plates will be seen collected . 
into large heaps in which the individual blood-plates 
may still be recognized. In a few minutes the 
plates fuse together into a granular mass which be- 
comes vacuolated, and at this moment coagulation 
begins. From the periphery of the granular heaps 
hundreds and thousands of fine processes radiate, and 
form a network which slowly spreads into the sur- 
rounding plasma. 
