There are many definitions of 'health'. They include:
Health depends on a number of factors, including biological factors, environmental factors, nutrition, and the standard of living. In other words, health can be seen as a function of welfare. Few of the issues which cause ill health are dealt with directly by 'health services'; they are, rather, issues in the 'welfare state' as a whole. When, in the 19th century, Chadwick identified poor health as a major cause of pauperism, his response was to improve sanitation, not to introduce more extensive medical care. Most of the world's diseases are attributable to poor water supply or nutrition. 'Health services' are better described as medical services.
There are clear differences in the incidence of ill health by social class. Figures from the UK show that people in lower social classes, including children, are more likely to suffer from infective and parasitic diseases, pneumonia, poisonings or violence. Adults in lower social classes are more likely, in addition, to suffer from cancer, heart disease and respiratory disease.
There are several possible explanations for these inequalities.
There are often major inequalities in access to health care according to social class. The problem becomes what Tudor Hart once called an 'inverse care law'; that those people in the worst health receive the least services. 
Health care can be divided into a number of different branches. Conventionally these include
Public health is probably the most important issue for the health of
a population; primary care is the main focus of medical care in
practice. Medicine in hospitals is probably the least important in
terms of its impact on health or illness, but it costs the most, has
the highest status and is the focus of most political attention.
That does not mean, however, that medical systems miss the point - they
are the point. What people mainly look for in a health system is
not health, but social protection in the event of illness; and a
national health care system offers, not health, but universal
Debates about "health services" are not just about health care. The term stands for a range of measures concerned with social protection. These measures typically include social insurance and solidaristic provision. In some countries (e.g. France) this is classified as a form of social security. Most countries in the OECD, with the main exception of the USA, offer universal coverage for the costs of medical treatment in hospital, and for at least part of the costs of ambulatory care. Payment for medical goods, such as pharmaceuticals, is much more uneven.
When people pay for social protection, their expectations are likely to be different from consumers paying for specific courses of treatment, like elective surgery. Typical issues in social protection are accessibility, coverage and the responsiveness of services, especially in emergency. These issues are different, and potentially more important for service users, than the kinds of issue which influence decisions in direct consumption, such as quality or the availability of alternative treatments. However, many debates in health care, such as arguments for "centres of excellence" in medical care or arguments for developing choice, ignore the former criteria in favour of the latter.
The focus on insurance and security implies a strong focus on financial issues. The combination of ageing populations, increasing expectations and demand, rising technical costs (or "medical inflation") and increasing costs of labour in developed economies have led to substantial increases in expenditure. State-provided care tends to be relatively cheaper than market-based provision, partly because of rationing, partly because consumer demand is less restrained, and partly because producers are less free to determine expenditure.
|An operating theatre in 1938. (c) Hulton-Getty collection.|
Medical care in the nineteenth century was principally private or voluntary. However, sickness was a primary cause of pauperism, and the Poor Law authorities began to develop 'infirmaries' for sick people. The number of infirmaries grew very rapidly after the foundation of the Local Government Board, because of the influence centrally of doctors.
The demand for the infirmaries was at first resisted by a deliberate emphasis on the stigma of pauperism, of which the main legal consequence was the loss of the vote. Few people who became paupers had the vote, but after the extension of the franchise in 1867 and 1884, the numbers increased dramatically. In 1885, the law requiring people to be paupers before using the infirmaries was abolished.
Prior to 1948, health services were mainly based on three sources:
These were unified when the NHS was formed in 1948.
Aneurin Bevan, founder of the NHS.
(c) Hulton-Getty collection.
The right to welfare. The NHS is seen by many people as the core of the 'welfare state'. People receive health care as a right. There is no right to health care on demand. The principal rights are a right to be registered with a general practitioner, and the right to be medically examined, though out of practice hours that has been substantially delegated to NHS 24, a telephone-based service. There is no formal right to receive any treatment. This is within the discretion, or 'clinical judgment', of the doctor.
Comprehensiveness. The NHS is held to protect all citizens.
Access to health services depends on registration with a general
practitioner. Homeless people in particular have great difficulty
gaining access to primary care, because without an address it is
generally impossible to register.
The service itself has never been comprehensive. The NHS does ration resources according to priorities. Not only are there not regular checkups for everyone, but there are long waiting lists, and people with quite serious needs - like those from the 1950s onwards needing renal dialysis - may die, because the cost of treatment is greater than the NHS is ready to bear. NICE, the National Institute for Health and Clinical Excellence, approves medicines for use on the basis of the cost per Quality Adjusted Life Year or QALY; approval seems to depend on cost not exceeding £20-30,000 per QALY, though the level is higher for end-of-life care.
A free service at the point of delivery. The initial idea was that no-one should be deterred from seeking health services by a lack of resources. Charges were first introduced by the Labour government in 1950. They were substantially increased by the Conservative government after 1979. The 1988 Act removed free eye tests, later restored in Scotland.
The NHS offers all citizens - whether or not they actually use the
service - the equivalent of medical insurance. This has a
clear and direct financial value, but that value is rarely
recognised, and it does not feature in national income or distributive
Nurses demonstrate over low pay, 1982.
(c) Hulton-Getty collection.
Throughout its history, the NHS has been dominated by the hospital services, in particular by the high-status university hospitals. The bulk of expenditure on the NHS (over 70%) goes on hospitals. General practice, though it deals with the vast majority of reported illness - probably over 95% - accounts for less than 10% of spending.
The NHS inherited a maldistribution of resources, especially in London. where the main hospitals were concentrated in the centre of the city. London's lack of adequate primary care coverage and over-reliance on hospitals for treatment have created recurring problems. The Labour government in the 1970s attempted to redress the balance by transferring resources from hospital care to primary care, limiting the growth of better served regions, and favouring the development of some underfunded specialties, like medicine for the elderly. This led to hospital closures. The policy was continued by the Conservatives in the 1980s.
Complaints about the NHS tend to focus on the problems of hospitals: waiting lists, lack of spare capacity, and 'shroud-waving' in response to spending controls. The severity of the problems is possibly exaggerated. Enoch Powell, a former Minister for Health, commented on "the continual, deafening chorus of complaint " which characterises the NHS. By contrast with the private sector, where people always pretend that things are better than they are, the system of finance in the NHS "endows everyone providing as well as using it with a vested interest in denigrating it. " 
Initially, the NHS had a tripartite (three-part) structure, with three branches - hospitals, primary care and local authority health services. In 1974, a 'unified' structure was introduced, with three main levels of management, at Regional, Area and District level. The 1974 reorganisation led to a great deal of disruption, and was heavily criticised. Following political disagreements, Area Health Authorities were abolished in 1982 - throwing out of the window ideas like local integration of services and co-ordination with social services authorities.
In the 1980s, Enthoven, an American economist, made an influential
criticism of the NHS, arguing that it was inefficient, riddled with
perverse incentives and resistance to change.  The reforms which
followed were based in the belief that the NHS would be more efficient
if it was organised on something more like market principles. Enthoven
argued for a split between purchaser and provider, so that Health
Authorities could exercise more effective control over costs and
production. The NHS administration was broken up into quasi-autonomous
trusts from which authorities bought services. The role of Regional
Health Authorities was taken over by 8 regional offices of the NHS
management executive. For the first time, Klein comments, the NHS
became truly a nationally administered, centralised service. 
In principle, the Labour government removed the internal market. In
practice, it retained its main elements - the purchasing role of health
authorities, the provider trusts and GP commissioning. The reform of
services in 2002 replaced the English Regional Health Authorities and
District Health Authorities with 28 new Strategic Health Authorities
and 310 Primary Care Trusts; the number of SHAs was reduced to 10 in
2006. These authorities were abolished in the 2012 Health and Social
Care Act, which relies on the role of a large number of "Clinical
Commissioning Groups" in their place. Central control has passed
from the Department of Health to NHS England and Monitor, the health
There are conflicting accounts of problems with the current structure. One set of criticisms is concerned with 'command and control' from the centre. The Francis report on the Mid-Staffordshire hospitals points to an inappropriate focus on government-led financial control and targets at the expense of patient care. Another set of criticisms concerns the emphasis on commercialisation and sub-contracting. In England, routine service provision is now governed through commissioning and detailed contracts; most contracts since 2012 have been awarded to private providers. "Choice" in the market is not only choice for a patient; it also implies choice for the provider, and selective market provision may be inconsistent with the broader objectives of the NHS. It is not clear, however, whether both types of criticism - centralised control and market-based fragmentation - can be valid at the same time.
J Naidoo, J Wills, 2008, Health studies: an introduction
Basingstoke: Palgrave Macmillan
A Mahon, K Walshe, N Chambers, 2009, A reader in health policy and management, Maidenhead: Open University Press
Health services, from the British Library's Social Welfare Portal