acute hepatitis or cirrhosis, this being more common in those cases where the jaundice relapses and convalescence is prolonged.A few cases have also been reported wvhere, after an interval of several years of normal health, clinical cirrhosis has supervened, and, while the evidence that the cirrhosis in these cases is due to antecedent hepatitis is not absolute, it can certainly be considered as highly suggestive.
Preface to First Edition THIS book does not attempt to review the literature upon bacterial cytology, of which the bulk is very great and the value, in many cases, difficult to assess. The bibhography is confined to a relatively small number of works, almost all recent. No attempt has been made to supply references for analytical discussion or general information. The purpose is rather to present a reasoned case for regarding bacteria as living cells with the same structure and functions as other living cells, and to correlate the available information upon the various types of bacteria. Bacteria, as living creatures, have been little studied. It is their activities as biochemical or pathological agents which have received almost undivided attention. Even these problems, however, cannot fail to be clarified by a better knowledge o{ the organisms responsible. It is also hoped that biological workers in other fields may profit by contact with this, largely unknown, body of evidence, and may find the comparisons and analogies useful and stimulating in their related studies. I have attempted, as far as possible, to base my arguments upon my own observations, or upon such information as I have been able personally to confirm. Where I have not had die opportunity to do so, I have tried to indicate clearly the status of the argument. K. A. B.
SUMMARY:The cell wall of growing Gram-negative bacteria is formed mainly, or entirely, at one pole of the cell. At this point the cell wall is soft and transparent to the electron beam, and there is a concentration of stainable material in the underlying cell membrane. A similar 'growing point' occurs at the point of cell division. In dividing bacteria, the portion of the surface which bears the flagella is retained in its entirety by one daughter cell, the other daughter cell grows new flagella.In the course of an investigation of the growth of bacterial flagella (Bisset & Hale, 1951) it was observed that the flagella tended to develop at one pole of the cell in the process of germination from the microcyst stage. It was also observed that, in dividing cells of Salmonella typhi, one daughter cell was usually flagellated while the other was not. This phenomenon was further examined, and observations were made upon Proteus vulgaris and Pseudomonm JZuorescens.
METHODSElectron microscopy and silver impregnation stains for photomicrography were used, exactly as in the foregoing study (Bisset & Hale, 1951).
OBSERVATIONSPreparations were made of young cultures from 2 to 24 hr. old. When the original inoculum consisted of non-flagellated microcysts (Bisset, 1950) cell division commenced shortly after germination and was active after 3 or 4 hr. Salmonella typhi. Dividing cells first elongated considerably, and in this condition it was already apparent that almost all flagella were confined to onehalf of the cell (Pl. 1, figs. 1-3). When division was complete all the flagella remained on one daughter cell, the other being quite devoid of flagella or just commencing to produce them (Pl. 1, figs. 4, 5).Proteus vulgaris. This bacterium divided in a similar manner, but there was a significant difference from the condition in Salm. typhi. The original flagella were retained upon one half of the growing cell, but new flagella began to develop upon the other half before division was completed. Thus in a bacterium which was on the point of division, or had just divided, one daughter cell usually had much longer flagella than the other (Pl. 2 , figs. 6-9).Growing points. The conclusion from these observations upon the behaviour of the flagella in dividing bacteria is that the cell wall and flagella-bearing structures are produced a t one pole of the cell. This was borne out by the appearance of the cell wall in electron micrographs. Nearly always the pole distant from the flagella was soft and transparent in appearance. This can be
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