The latter smells faintly of ethanol; a 1% aqueous solution has a pH of 2–3; and the specific rotation is 
  
    
      
        [
        α
        
          ]
          
            D
          
          
            25
          
        
      
    
    {\displaystyle [\alpha ]_{D}^{25}}
   −110° cm³/dm·g in 0.01 N methanolic hydrochloric acid. History
After penicillin revolutionized the treatment of bacterial infections in WWII, many chemical companies moved into the field of discovering antibiotics by bioprospecting. American Cyanamid was one of these, and in the late 1940s chemists there discovered chlortetracycline, the first member of the tetracycline class of antibiotics. Shortly thereafter, scientists at Pfizer discovered terramycin and it was brought to market. Both compounds, like penicillin, were natural products and it was commonly believed that nature had perfected them, and further chemical changes could only degrade their effectiveness.
Catamenial pneumothorax is a spontaneous pneumothorax that recurs during menstruation, within 72 hours before or after the onset of a cycle. It usually involves the right side of the chest and right lung, and is associated with thoracic endometriosis. A third to a half of patients have pelvic endometriosis as well. Despite this association, CP is still considered to be misunderstood as is endometriosis considered to be underdiagnosed. The lack of a clear cause means that diagnosis and treatment is difficult. The disease is believed to be largely undiagnosed or misdiagnosed, leaving the true frequency unknown in the general population. Catamenial pneumothorax is defined as at least two episodes of recurrent pneumothorax corresponding with menstruation. It was first described in 1958 when a woman presented with 12 episodes of right-sided pneumothorax over 1 year, recurring monthly with menstruation. Thoracotomy revealed thoracic endometriosis.Many patients present with chest pain close to their menstrual periods. Surgical exploration can be used in an attempt to visualize the problem; mechanical pleurodesis or hormonal suppressive therapy can also be used. Sometimes, a second surgical look can show fenestrations in the diaphragm. Due to the fact that endometriosis has been attributed to retrograde menstruation, upwards of 90% of women may have an immune deficiency. This prevents clearance of endometrial cells from the peritoneum. Endometriosis is defined as tissue similar to the endometrial tissue that has implanted outside of the uterus.