302 TEXT-BOOK OF BACTEEIOLOGr. 



exist for each or any number of attacks according as there appear 

 onlj' one or several successive generations of plasraodia. 



Golgi is of tlie opinion that the diverse forms of malaria (as 

 tertian and quartan fever) are not caused by one and the same 

 Plasmodium, but by two dilferent, morphologically distinct sub- 

 species. But this is by no means generally admitted or confirmed. 

 It must be confessed that the striking multiformity exhibited by 

 the Plasmodia rather contradicts this view. Danilewsky, an expert 

 investigator in this domain, formerly entertained similar views. 



Be this as it may, the investigations made at the most different 

 locations and by very reliable men (thus in France and the French 

 colonies by Laveran, in Italy by the above-named observers, in 

 Russia by Sacharoff, Metschnikoff, and Chenzinsky, in America by 

 Councilman and Osier, in Germany by Plehn, in Austria by Paltauf) 

 have shown that there is found in the blood of persons afflicted 

 with malaria a peculiar micro-organism, appearing in the interior 

 of the red blood-corpuscles, which by its morphological and other 

 appearances must be ranged among the sporozoa or gregarines. 

 Its regular and exclusive occurrence in malaria, as also the cir- 

 cumstance that it disappears under the influence of specific treat- 

 ment — i.e., after the use of quinine — hardly admit of a doubt that 

 we have here the exciter of the affection. 



The significance of the Plasmodia (especially from a diagnostic 

 point of view) appears to be quite extraordinary, and renders it de- 

 sirable that our knowledge concerning this important micro-organ- 

 ism be soon perfected. Only when we shall succeed in artificially 

 cultivating the malaria parasites and using them for experiments 

 of transmission shall we be able to obtain a clear insight into the 

 pathology and epidemiology of this disease. 



XV. PNEUMOCOCCUS (PRIEDLANDER). 



Just at a time when a parasitic cause was presumed to exist 

 for many morbid conditions of the human body (science being still 

 quite deficient in tangible, actual proofs of this opinion), intelligent 

 observers asserted that pneumonia, too, the genuine infiammation 

 of the lungs, belonged to the class of such affections. " Catching 

 cold " had always been regarded as a decisive cause of pneumonia. 

 The keen eye and clear judgment of such investigators as Jiirgensen 

 deserve great praise for discerning its infectious cause from its 

 appearance and symptoms. 



This standpoint appeared to be confirmed by the investigations 

 published in 1883 by Friedlander and Frobenius regarding a special 



