THE NOEMAL CONJUNCTIVA 37 



I have often seen albicans organisms, which from slow growth have appeared 

 as thicker, whiter, and shining cultures, though only as isolated colonies. 



The organism which Bach and Basso described as Micrococcus concentricus is 

 characterized by the very definite concentric marking of its flat slightly iridescent 

 colonies. I have sometimes cultivated this organism ; it is comparatively rare. 



White Staphylococci, markedly pyogenic and thoroughly deserving that title, 

 which rapidly liquefy gelatine, and in small numbers produce a purulent keratitis, 

 are rare ; very few of the cocci described in the literature under this name can be 

 certainly identified as such. A certain number of the cocci described as Staphylo- 

 coccus pyogenes albus and Micrococcus pyogenes albus belong to this group ; how 

 large a number cannot be stated with certainty. My own experience of a large 

 number of conjunctivas has been that a markedly pyogenic Staphylococcus pyogenes 

 albus is rare in the normal conjunctiva. 1 Heim ('LehrbuchderBakt.,' 1906) states 

 that he has never obtained the Staphylococcus albus from pas, and contrasts with 

 the Staphylococcus pyogenes aureug the ' skin cocci,' which the common con- 

 junctival cocci so strongly resemble. I quote this opinion as one of many, only to 

 illustrate how, in this respect, the conjunctiva presents analogies to the sur- 

 rounding skin. 



Amongst the colonies designated by many authors as Staphylococcus 

 pyogenes aureus (Eosenbach), there are some which do not merit this 

 game. Their diagnosis should not been made so rapidly as is often 

 the case, merely on account of the yellow or orange-yellow colour. 2 

 A mistake here is far less frequent than in the case of the white cocci 

 of the conjunctiva, for the majority of such orange-yellow colonies do, 

 as a matter of fact, prove to be the pyogenic form with the well- 

 known characteristics, of which I will only give a summary : 



Eound cocci of variable size, averaging 0'7 to 0-9 /j. (Giinther) in diameter, though 

 in many purulent effusions larger or smaller (cf. p. 236), multiplying by fission. 

 (Individuals dividing appear as Diplococci, and though when deeply stained appear 

 round cocci, when faintly stained may show the line of cleavage.) They usually lie 

 in clusters, and stain deeply by Gram's method. Growth occurs on all common 

 media, even if weakly acid, at room temperature or hi the incubator. 



On agar or blood-serum round raised colonies, with smooth edges, develop. Under 

 the microscope they appear coarsely granular. Macroscopically after twenty-four 

 hours' growth (aerobic) moist, glistening, greyish-white colonies appear, and in the next 

 few days take on a bright orange-yellow colour, the depth of which and the rapidity 

 of tys development vary with different strains. Many develop the colour more quickly 

 when daylight is excluded. 



When kept for long in a bright light, on the contrary, the colour fades completely. 

 It is retained for a longer time in the dark. (This occurs in preserved cultures.) 

 After continued propagation the formation of colour gradually diminishes, and in 

 the end completely disappears. 3 It can be recovered by passage through an animal, 



1 I have been able to gain a large experience on this question, seeing that many 

 investigators doing bacteriological work in my laboratory begin with the normal con- 

 junctiva, especially their own, and conduct virulence tests of the organisms found. Thus 

 I am able often to demonstrate in my clinic the relatively harmless nature of the con- 

 jimctival organisms. 



' 2 M. Neisser makes the same criticism of the recorded findings in the air, etc. 



3 Leber has observed these colour variations. Many writers would explain aureus and 

 albus as varieties, each of which can be transformed into the other. 



