160 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



retained. It grows readily on blood-serum, which is rapidly 

 liquefied. 



Of the rarer causes of conjunctivitis, the staphylococcus, 

 streptococcus, and pneumobacillus may be mentioned. The 

 latter may be recognized by the presence of a capsule sur- 

 rounding a bacillus which greatly resembles an elongated 

 pneumococcus, which does not retain Gram (Plate III., Fig. 3). 



Diphtheria affects the conjunctiva, and its clinical recogni- 

 tion is not usually difficult. But the' bacteriological diagnosis 

 (without the use of animal inoculations) is complicated by the 

 fact that an organism the xerosis bacillus which closely 

 resembles the diphtheria bacillus may occur in the 4 conjunctiva 

 either in health or in disease. It does not appear that the two 

 can be differentiated with certainty by morphological appear- 

 ances, staining reactions (the xerosis bacillus often shows 

 polar granules), or even by cultural tests. The xerosis bacil- 

 lus is believed to be a harmless saprophyte. 



In tuberculosis of the conjunctiva it is usually necessary to 

 excise a piece of the lesion, and cut sections, but bacilli have 

 been detected occasionally in scrapings. 



THE SPUTUM 



The chief applications of bacteriology to the examination of 

 the sputum have been mentioned already, but it seems advis- 

 able to add a few general words on the subject. 



The selection of the material is of prime importance, since 

 it is obviously useless to expect an examination of the secre- 

 tion of the mouth and fauces to yield information as to the 

 state of the lungs. Where the sputum is copious the danger 

 of this error is not great ; in advanced phthisis the contents of 

 a sputum-cup taken at random will usually show signs of 

 tubercle bacilli. Where the sputum is but, scanty the pos- 

 sibility is great, and in this case the patient should be supplied 

 with a clean (and, if possible, sterile) sputum-cup, to be used 

 only for collecting the material for examination, and he must 

 be instructed to use it only after a paroxysm of coughing, and 

 when he distinctly feels the sputum come up from the chest. 

 If the patient is not sufficiently intelligent, the task of collect- 

 ing the sputum may be entrusted to a nurse, to whom the im- 



