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PROGRESS OF MICROSCOPICAL SCIENCE. 
but also osteoclasts. The osteoclasts, then, do not arise from pre- 
existent osseous or dental tissue ; and Kolliker believes that they 
belong to the same category as the osteoblasts, which perform an 
important part in the formation of bones. His reasons are as follows : — 
First, transitional forms are observed. Secondly, most of the osseous 
surfaces, which at the time when absorption takes place are covered 
with osteoclasts, originally present osteoblasts ; and the gradual 
intrusion of the former among the latter can be noticed by direct 
observation. Thirdly, osseous surfaces that have been undergoing 
absorption may again take on growth ; and then there is a re-forma- 
tion of osteoblastic cells, partly through the splitting up of the 
multinucleated osteoclasts. This is observed in the jaws. Before 
and at the commencement of the formation of the teeth, the lower jaw 
shows osteoblasts in the situation of the future dental groove. After 
this, when the dental sacs and teeth are being formed, the bony 
substance is removed, and a large furrow is formed in the jaw. Lastly, 
when the eruption of the teeth takes place, there is again a formation 
of bone at their roots, leading to the development of the alveoli. As 
to the manner in which the osteoclasts are concerned in the removal 
of bone, Kolliker has not arrived at a definite conclusion ; but he 
considers the following points worthy of note : — 1. The removal does 
not consist in an absorption of the earthy matter as in osteomalachia ; 
it seems rather, that both the organic and the inorganic material are 
removed simultaneously. 2. The removal of the hard tissue is not 
preceded by crumbling, but takes place gradually, leaving the bone 
with well-defined and smooth edges and surfaces. 3. The surface of 
bones undergoing absorption, where osteoclasts are present, have not 
an acid reaction. 4. Two experiments, made in order to ascertain 
whether the osteoclasts yielded any slightly acid or alkaline material 
having a solvent action on the bones, were attended with negative 
results. 5. In many cases the osteoclasts present clusters of fine 
short hairs or filaments on the side in contact with the bone. 
The Microscopy of the Blood in Syphilis . — We have already alluded 
to this subject. However, the ‘Lancet’ has taken the matter up also, 
and it gives (June 22) an excellent leading article upon it. Dr. Los- 
torfer, who, it seems, was specially involved in the matter, has supplied 
Strieker’s ‘ Medizinische Jahrbucher’ with the facts which have led him 
to the position he has now taken up on the affirmative side of the ques- 
tion. He was supplied, it appears, by Strieker, who appends a note to 
the paper, with a number of test specimens ; and arrived, on the whole, 
at very correct conclusions. A drop of blood was taken from the skin, 
and as quickly as possible placed upon a clean object-glass, and 
covered. Twelve glasses, with drops belonging both to syphilitic and 
non-syphilitic patients, and properly numbered for subsequent identifi- 
cation, were then placed in a moist chamber, and were examined from 
day to day with a Hartnack’s immersion No. 10, ocular No. 3. During 
the first day or two, vibrios, bacteria, and the early stages of develop- 
ment of sarcina, were commonly met with. On the third, or still 
more frequently on the fourth or fifth day, and occasionally even after 
twenty -four hours, small bright corpuscles made their appearance, 
