176 BIOLOGY AND TECHNIQUE 



The routine examination of spinal fluid is best made upon the sedi- 

 ment of centrifugalized specimens. The microorganisms with which we 

 deal most frequently in this fluid are the meningococcus, the pneumococ- 

 cus, the streptococcus, and the tubercle bacillus. If morphological ex- 

 amination reveals bacteria resembling the first three of these in appear- 

 ance and staining-reaction, surface smears should preferably be made 

 upon plates of serum agar, blood agar, or upon tubes of LoefHer's co- 

 agulated blood-serum. Failure to find organisms morphologically does 

 not exclude their presence and careful cultivation should be done in all 

 cases. When organisms are not found by simple morphological examina- 

 tion and the fluid and sediment are scanty, specimens should be stained 

 by the Ziehl-Neelson method for tubercle bacilli. In such cases it is 

 often of advantage to set away the specimen until a thin thread-like 

 clot of fibrin has formed in the bottom of the tube. In smears of such 

 a clot, tubercle bacilli are found with far greater ease than they are found 

 in centrifugalized specimens. If these examinations are without result, 

 inoculation of guinea-pigs should be resorted to. 



Examination of Urine. — Bacteriological examination of the urine is 

 of value only when specimens have been taken with sterile catheters, 

 and care has been exercised in the disinfection of the external genitals. 

 Many of the numerous finds of bacillus coli in urine are unquestionably 

 due to defective methods of collecting material. Urine should be cen- 

 trifugalized and the sediment examined morphologically and pour- 

 plates made and surface smears made upon the proper media. If 

 necessary, animal inoculation may be done. In examining urine for 

 tubercle bacilli, special care should be taken in staining methods so 

 as to differentiate from Bacillus smegmatis. 



Examination of Feces. — Human feces contain an enormous num- 

 ber of bacteria of many varieties. Klein,' by special methods, es- 

 timated that there were about 75,000,000 bacteria in one milligram 

 of feces. It has been a noticeable result of all the investigations upon 

 the feces, that although enormous numbers can be counted in morpho- 

 logical specimens, only a disproportionately smaller number can be 

 cultivated from the same specimen. This is exphcable upon the ground 

 that special culture media are necessary for many of the species found 

 in intestinal contents and upon the consideration that many of the 

 bacteria which are present in the morphological specimen are dead, show- 

 ing that there are bactericidal processes going on in some parts of the 



' Kkin, Ref. Cent. f. Bakt., I, xxx, 1901. 



