342 BACTEKIOLOGY OF THE EYE 



of the tubercular form of leprosy. On account of their predilection to 

 the early occurrence of the nodules and the spots, the eyebrows are 

 the common site for diagnostic excisions. In the tubercular form the 

 diagnosis is completed by an incision into the infiltrated tissues, and 

 the examination of the expressed fluid for the lepra bacilli. (For 

 staining methods, see p. 17.) 



The nodes begin in the middle layers of the corium. Generally, 

 but not invariably, a blood or lymph vessel can be seen in the middle 

 of the node ; the bacilli mostly lie in the cells of the intima, less often 

 in the leucocytes. The reaction begins in the tissues after the bacilli 

 have found their way through the vessel walls, and is usually less 

 marked than in the case of tuberculosis. The bacilli spread into 

 the neighbouring cells, but do not show such a destructive effect upon 

 them as do the tubercle bacilli, and well-nourished cells showing 

 karyokinetic figures may be found with lepra bacilli in their immediate 

 neighbourhood. The lepromata present the appearance of being true 

 solid tumours. Large epithelioid cells containing many bacilli are 

 common, and are -considiered by Lie to be derived from wandering 

 cells ; these form the so-called lepra cells, and are always very 

 plentifulin the central oldest part of the nodule. 



The muscle cells (often pigmented) of the tunica media of the blood- 

 vessels are generally much freer from bacilli than are the overgrown 

 and sclerosed cells of the intima and adventitia. In general, muscle 

 and elastic fibres are poor in bacilli. 



In the leprous nodules, especially in the cornea, a new formation of 

 vessels is often observed. 



Here and there a small nerve may be seen in the middle of an 

 avascular nodule, and numerous bacilli will be found in its endo- 

 neurium, perineurium and sheath of Schwann. Those in the sheath 

 of Schwann often lie in spindle-shaped clusters. According to Lie, 

 this arrangement is not. due, as many maintain, to the bacilli being in 

 lymph spaces, but, as can easily be shown, in teased preparations, 

 to the bacilli lying in the cells of the nerve. 



The nerves thus retain their normal structure for a long time, and 

 the nodules their normal sensibility. After a considerable time they 

 certainly become just as anaesthetic as the spots in the anaesthetic 

 form. 



The nodules gradually coalesce, and thus diffuse nodular thicken- 

 ings are formed. 



The epidermis of the skin remains intact for a relatively long time. 

 As soon as the rete mucosum is attacked, there is a defective forma- 



