THE health of Wang Juntao, serving a 13-year jail term for allegedly being a ''black hand'' behind the 1989 anti-government demonstrations, is deteriorating in confinement at a prison hospital, friends said. Doctors have discovered that Wang, who has long suffered from hepatitis B, has also developed coronary heart disease. The 34-year-old may also have contracted diabetes, cirrhosis or a kidney disease, the friends said. Since September 1991 Wang has been at the Yanqing prison hospital 80 kilometres northeast of Beijing. He has repeatedly pressed for better medical treatment. Over the past two months, the prison has allowed him several visits to specialist hospitals in Beijing, each time for less than a day. The authorities at Yanqing refuse to allow him to leave the prison hospital. One of the doctors told Wang that he would not have accepted the dissident had he known the seriousness of his physical condition, the friends said. Conditions at the prison hospital are poor, and Wang is not getting proper treatment, his wife, Ms Hou Xiaotian, said. As a result, his health has failed to improve, she has maintained. Over the past few days Ms Hou has written to the Communist Party Politburo Standing Committee asking that Wang be allowed out on bail for medical treatment. Earlier requests fell on deaf ears. The sources also said that on two occasions in February and March, Ms Wang Zhihong was allowed to live with her husband, dissident Chen Ziming, in jail for two days each time. Ms Hou also requested to stay with her husband in jail for a short time. But she was turned down. Meanwhile, a German human rights delegation said the Chinese assertion that all students arrested in connection with the Tiananmen crackdown had been released ''was not satisfactory''. The team from the sub-committee for Human Rights and Humanitarian Aid of the German Parliament visited Beijing and Shanghai early this month. Member Mr Heribert Scharrenbroich said in Bonn that the committee told Chinese officials that human rights discussion with China would not abate as long as persons were detained for political or religious reasons. According to the German Consulate in Hongkong yesterday, the delegation demanded the release of several prisoners whom the sub-committee considered to be victims of political and religious persecution.