6 THE MORPHOLOGY OF BACTERIA 



conidia of the actinomyces which are definitely reproductive elements and serve to 

 perpetuate the species. It is debatable whether it is advisable to employ such an anal- 

 ogy since Drechsler has pointed out that the actinomyces form a group closely related 

 to, and possibly forming a subdivision of, the hyphomycetes. Knoblike protrusions 

 have been observed in many species of bacteria, and certain authors have come to re- 

 gard them as conidia, thereby claiming a complicated cycle of development for the 

 ordinary simple bacteria. Almquist, Enderlein, and Fuhrmann have emphasized this 

 phase of development. Thus Almquist' has found, in cultures of the typhoid bacillus, 

 the dysentery bacillus, and the cholera vibrio, spherical or globular elements and 

 giant cells, often with distinct internal structure, from which normal forms are regen- 

 erated. The transformation of these aberrant forms to the normal has been observed 

 directly under the microscope by Almquist. Similar observations have been made in 

 this country by Lohnis, Mellon, and Bergstrand, with diphtheria bacilli and with 

 streptococci. 



Large spherical bodies had previously been observed by Swellengrebel in the larger 

 spirilla but were regarded by him as no longer capable of multiplication. The ability 

 of these knoblike protrusions and spherical bodies to regenerate normal individuals 

 may be regarded as practically settled in view of Almquist's observations, but the in- 

 terpretation of these bodies as true conidia can hardly be accepted at the present 

 time. Almquist and Lohnis have further described a kind of sexual multiplication, 

 consisting of conjugation or amalgamation of two forms. Interesting as such observa- 

 tions may be, real proof for sexual multiphcation in bacteria is still lacking. It should 

 be remembered, however, that if bacteria continue to multiply indefinitely without 

 some kind of change which represents conjugation they form an exception to the laws 

 governing other free-living plants and animals. 



INTERNAL STRUCTURE 



The characteristics of the internal structure of the simpler bacteria have been the 

 subject of investigation since the earliest days of bacteriology, with particular refer- 

 ence to the question of nuclear material. Opinions have ranged from the view that the 

 entire cell represents the nucleus of higher cells to the view that no true nuclear 

 material is present in them. Chemical analysis has thrown much light upon the 

 kinds of chemical substances present in the bacteria, and the chemical demonstration 

 of nuclear material has stimulated bacteriologists to approach the question again and 

 make use of the more refined staining methods devised by the cytologists. As a re- 

 sult, a kind of diffuse nucleation was established for the bacteria, nuclear material 

 (chromatin) being distributed through the bacterial cytoplasm. Certain authors like 

 Nakanishi' and Dobell,^ however, have always claimed the presence of true mor- 

 phological nuclei. Thus Nakanishi has described minute spherical bodies in Staphylo- 

 coccus aureus, in the middle of the cells, which he regards as nuclei. Dobell found 

 true morphological nuclei in a spiral organism which he named Paras pii ilium vejdov- 

 ski, but which was not cultivated. There is still some doubt whether Dobell's organ- 



■ Almquist, E.: Ztschr.f. Ilyg. u. Infektionskrankh., 83, i. 1917. 



2 Nakanishi, K.: Centralbl.f. Bakleriol., 30, 145. 1901. 



3 Dobell, C. C: Arch.f. Proiist., 24, 907. 1912. 



