SYPHILIS. 27 



ages point to successive blood infections. Similar considerations 

 apply to the serous sacs; but few bacilli are found in the effusions 

 they contain when they have been infected by the blood stream. 

 When meningeal symptoms are present, bacilli are sometimes 

 to be found in the arachnoid fluid. 



The difficulty in obtaining bacilli from the blood stream in 

 general tuberculosis may be explained by the consideration that 

 the bacilli do not continuously circulate, but are soon entangled 

 and settle down. 



Disseminated tuberculosis may also spread by means of lym- 

 phatic vessels. The lymphatic stream is sluggish, and the 

 obstructions are numerous, so the miliary tubercles are mostly 

 seen near the original focus and have not the wide distribution 

 which is met with when the blood stream carries the infection. 

 Lymphatic dissemination may be seen when tuberculosis is 

 spreading from foci in the lung. It may also be observed when 

 tuberculosis is invading the lung from a bronchial gland, the 

 spread in this instance being retrogressive. It is possible that 

 the nodular forms of tuberculosis of serous membranes and 

 spleen are the result of lymphatic infection, and that this form of 

 infection may precede and originate a general blood tuberculosis. 



SYPHILIS. 



Syphilitic infection is favoured by damage to the surface 

 epithelium, for it is probable that the virus of syphilis invades 

 the intra-epithelial lymphatics at the point of inoculation. 

 A surface lesion may be absolutely necessary before the 

 lymphatics of the thick skin covering such parts as the finger or 

 cheek become infected, but in parts where the epithelial 

 covering is more delicate, as, for instance, the conjunctivas, 

 abrasion may not be a necessary antecedent. Tattooing affords 

 an easy method of inoculation, and the readiness with which a 

 cracked lip or a bite may become infected also bears witness to the 

 vulnerability of the tissues when their epithelial covering has 

 been damaged. During the period of lactation the nipple often 



