It is evident from this work and from the work of others that organisms having diphtheroidal morphology are wide-spread in their distribution in the human body. They are readily isolated from miscellaneous skin lesions, probably thriving better in pathological soils as saprophytes than in normal skin, although they can be obtained quite easily from the latter. Various strains can also be cultivated from the air, at least in this environment.

Aside from the air and superficial parts of the human body, diphtheroids have frequently been isolated from the deeper regions. Hoag, working on general paresis and certain conditions of the lung, cultivated 199 diphtheroids, the majority of which were from the lungs and respiratory tract, also in some instances from the liver and spleen. He considered 146 of these isolations to be identical and classified them as organism x. Robertson, McRae, and Jeffry likewise in cases of dementia paralytica isolated what they considered an identical strain which was closely related to the Klebs-Loeffler bacillus, from the inflamed ileum, stomach, tonsils or pharynx, bronchi, lung, and brain. They differentiated their organism from Bacillus hoffmanni and Bacillus xerosis.

The fact that these organisms have a somewhat unusual morphology, resembling as they do an organism of known pathogenicity, namely. Bacillus diphtheriœ, should form no basis for assuming that they, too, are apt to possess these qualities. When we consider the number of simple bacillary contaminators analogous to such organisms as Bacillus anthracis, Bacillus typhosus, etc., we can readily see how frequently this occurs.

The majority of the diphtheroids isolated by us stai??? by Gram's method; nearly all fail to resist the standard acid-fast methods, although use of the very low strengths of mineral acids allows the fixed stain to remain in whole or in part. There is consequently nothing unique in their tinctorial properties.

These bacillary strains differ considerably in their powers of cultivation. While the majority grow readily upon the ordinary laboratory foodstuffs, others require special products for their growth and still others cannot be grown even where special effort has been made. The fact that many strains grow slowly no doubt enhances their consideration as disease producers, as it seems to argue their difficult adaptation from their preëxisting site to an artificial environment. This reasoning does not apply when we consider the numerous causal agents that can so readily be cultivated directly from the diseased tissue, and again the fact that many saprophytes in their natural habitat are incapable of growth in vitro (figure 1).

The most striking of the biological features of these cultures is their wide range of pigment production. While many are white or creamy white, the majority range from a canary yellow to a distinct crimson, and one of the cultures recovered from a leper was a very deep dusky red or garnet. Numerous combined shades of yellow and pink, including such colors as salmon and orange, were present. Some cultures were distinctly pink, others varied in depth of color to a crimson. While many cultures of identical colors were obtained, the majority of strains showed some slight variance of shade.

While, of course, the inoculation of diphtheroidal cultures produces varying degrees of localized inflammation if employed in sufficient dosage, probably for the two-fold reason of acting as a foreign body and liberating proteolytic substances, still the diphtheroids isolated in the past have never been able to reproduce the clinical picture of the various diseases from which they were cultivated. The apparent reproduction of lesions in general paresis, in hepatic cirrhosis, and in leprosy does not form an ultimate postulate for the acceptance of organisms as specific etiological entities. This is evidenced by the fact that certain known saprophytic organisms when used as controls are capable of producing the same results.

It seems clear that organisms as broadly distributed as the diphtheroids should be suspected as contaminators when met in experiments bearing upon etiology. They should be viewed primarily in the same light as the staphylococcus and the various known contaminating bacteria. It is apparent that this type of organism has been regarded too much from the standpoint of pathogenicity. It is, of course, probable that among this large group there may be a few pathogenic types.

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