PNEUMONIA, MENINGITIS AND GONOEEHEA 329 



viable except under the most favorable of conditions. 

 Growth does not occur readily upon most of the ordinary 

 culture media. 



Physiology. — The meningococcus is killed readily by 

 drying. Small amounts of acid are produced from dex- 

 trose ; milk is not changed and gelatin is not digested. 



Pathogenesis. — The meningococcus apparently gains 

 access to the body through the respiratory tract. It finds in 

 many individuals a suitable site for growth in the naso- 

 pharynx, that is, the back portion of the nasal cavity just 

 above the pharynx. From this point in a rather uncertain 

 proportion of individuals the organism finds its way, per- 



FiG. 65. — Neisseria meningitidis. 



haps through the lymph channels or through the blood 

 stream, to the central nervous system, where it grows upon 

 and in the meninges (the membranes which cover the brain 

 and the spinal cord). This is followed by the usual evi- 

 dences of inflammation. The clear cerebrospinal fluid 

 becomes clouded with white blood cells, that is, it becomes 

 more or less purulent. A mount of this material secured 

 by means of a lumbar puncture, that is, by the insertion of 

 a hypodermic needle between the lumbar vertebrae into the 

 spinal cavity, shows more or less numerous Gram-negative 

 diplococci frequently lying within the white blood cor- 

 puscles. The disease is not infrequently accompanied by a 

 septicemia, that is, the meningococci gain access to the blood 

 stream and grow rather generally through the body. 



